Firewalls are absolutely vital for keeping network security in force. The firewall stops and controls the traffic that comes between your network and the different sites you go to. A firewall is a constituent of a company’s network protection, and it acts to keep in force the network security policy. It can log inter-network activity with efficiency. It can also reduce a network’s vulnerability. Whenever an organization is connected to the Internet but is not using a firewall, any host on the network has direct access to all resources on the internet. If you don’t have a firewall, every host online can attack every host in your network.

What is a Firewall Incapable of Doing?

Firewalls can’t always detect malicious data. For the most part they cannot offer any protection against an attack from inside, although they may log network activity should the criminal use the Internet gateway. A connection that doesn’t go through a firewall cannot be protected by a firewall. To put it another way, if you connect directly to the internet via modem, there is no way the network firewall can protect you. Some firewalls cannot protect from viruses. Firewalls also cannot totally protect against previously unknown attacks; while a simple firewall provides little protection against computer viruses.

Firewall User Authentication or Verification

You establish a claimed identity’s validity via user authentication. The use of a password and user name can provide this authentication; however, it is not really strong authentication. When you use a public connection, for example if you have a connection to the Internet that is not encrypted, your user name and password can easily be copied by other people and replayed. Powerful user authentication makes use of cryptography, for example SSL certificates. A certificate of this sort can prevent “replay attacks” from occurring. A replay attack happens when a user name and password are captured and used again to gain unauthorized access.

Firewall-to-firewall encryption

A connection that is encrypted is sometimes called a VPN, or Virtual Private Network. Cryptography makes this more or less private. Of course it isn’t really private. The information may be private but it is sent on a public network — the Internet. While VPNs were available before firewalls were, they became more common when they began running on firewalls. Today, most firewall vendors offer a VPN option.

Additional Purposes of Firewalls

• Increasingly, firewalls are being used for purposes of content filtration. Virus scanning is a common addition to firewalls in this area as well. Though this may be a waste of resources, because filtering for viruses needs to be carried out by every computer since information might be transmitted to these computers via routes besides through the firewall itself – for example, via separate disks.
• URL Screening: Firewall regulated accessibility to the internet as well as content filtering of both files and messages appears to be a practical extension of a firewall. The drawback of utilizing a firewall for URL or content filtering is minimized performance.
• To restrict the size of network space that any single user can occupy, or restrict the amount of the network’s bandwidth that may be utilized for given purposes.

Stephen Grisham, Sr. is a copy writer for InfoServe Media, LLC. InfoServe Media is a Houston, TX web design and web hosting company. Want to create your website yourself? InfoServe Media also offers a way to create a web site yourself with a very powerful and easy to use site builder. They also provide domain registration, search engine optimization (SEO) and more.

Article Source:http://www.articlesbase.com/security-articles/network-security-firewalls-810920.html

The firewall, a “combo” approach of software that regulates and monitors hardware and communications protocols, is there to inspect network traffic and all the “packets” of information that pass through to your inner sanctum, your CPU and hard drives. A firewall will rule out the possibility of harm, or at least greatly minimize, by noting and quarantining potentially harmful “zones” and will either deny or permit access to your computer based on the current set of rules that applies at the time, depending on many (very many) factors.

Basic tasks and settings

The basic task for a firewall is to regulate of the flow of traffic between different computer networks that have different “trust levels.” The Internet is full of countless overlapping zones, some safe and some totally deadly. On the other hand, internal networks are more likely to contain a zone or zones that offer a bit more trust. Zones that are in between the two, or are hard to categorize, are sometimes referred to as “perimeter networks” or, in a bit of geek humor, Demilitarized Zones (DMZ).

Without proper configuration, a firewall can simply become another worthless tool. Standard security practices call for a “default-deny” firewall rule, meaning that the only network connections that are allowed are the ones that have been explicitly okayed, after due investigation. Unfortunately, such a setup requires detailed understanding of network applications and a great deal of time and energy to establish and administer.

Who can do what?

Many businesses and individuals lack sufficient computer and network knowledge to set up a default-deny firewall, and will therefore use a riskier but simpler “default-allow” rule, in which all traffic is permitted unless it has been specifically blocked for one of a number of possible reasons. This way of setting up a firewall makes “mysterious” and unplanned network connections possible, and the chance your system may be compromised becomes much more likely.

Firewall technology had its first growth period in the computer technology revolution of the late 1980s, when the Internet was a fairly new in terms of its global reach and connectivity options. The predecessors to today’s hardware/software hybrid firewalls were the routers used in the mid 1980s to physically separate networks from each other. However small the Internet began, it was ultimately undone by supremely fast growth and the lack of security planning, and therefore there were the inevitable breaches caused by older (”prehistoric”) firewall formats. Fortunately, computer pros learn from their errors, and the firewall technology continues improving daily.

Cisco Kits is a leading provider of CCNA, CCIE and CCNP Cisco training courses and equipment. Visit online for more information on certification or just furthering education.

Article Source:http://www.articlesbase.com/networks-articles/why-firewall-security-is-necessary-to-protect-your-network-784872.html

 Today, the majority of application protocols use the Internet’s reliable Transmission Control Protocol (TCP). The functionality of TCP  is designed to be adequate not only for Internet applications but also for the variety of underlying networks.

           The protocol aims at providing a reliable service with the following features:

       1. Fairness to other flows that potentially share a channel’s bandwidth

       2. Dynamic discovery of current availability of bandwidth

• 1. Mechanisms for congestion avoidance and control and for optimization of  the error recovery process.

   Error control mechanisms are the central component of reliable protocols. They affect a protocol’s performance with respect to goodput, energy expenditure, and overhead. Error control is usually a two-step process: error detection, followed by error recovery . TCP assumes a relatively reliable underlying network where most packet losses are due to congestion . TCP  error control is centered on congestion losses and ignores the possibility of transient random errors or temporary blackouts due to handoffs and extended burst errors that are typical in wireless networks. TCP detects errors by monitoring the sequence of data segments acknowledged (received). When timeouts are correctly configured, a missing segment is taken to indicate an error, namely that the segment is lost due to congestion (i.e. buffer overflow). Reliable protocols usually implement an error recovery strategy based on two techniques: retransmission of lost segments; and downward adjustment of the sender’s window size and readjustment of the timeout period. When using TCP over wireless links results in congestion control measure being invoked at the source.

            The Additive Increase Multiplicative Decrease (AIMD) algorithm is used to implement TCP window adjustments; based on the analysis the algorithm achieves stability and converges to fairness in situations where the demand (of competing flows) exceeds the channel’s bandwidth .

            In a wireless network, however packet looses will occur more often due to unreliable wireless links than due to congestion. It is shown that the performance of TCP is sensitive to the packet size, and that significant performance improvements are obtained if a ‘good’ packet size is used. Packets on the internet may get lost either due to congestion, or due to corruption by the underlying physical medium. Given the low error rates of wired links, almost all losses are related to congestion. TCP’s reaction to looses is based on this very observation. Losses are detected either by timeouts at the source or by multiple duplicate acknowledgements ( dupacks ) from the receiver. TCP assumes that each packet loss is solely due to congestion. However, in a wireless network, TCP will encounter packet looses that may be unrelated to congestion. Nonetheless, these losses trigger congestion control measures at the source and severely degrade performance.   

TCP was designed and carefully calibrated to overcome the problems like as follows:

• 1. Stability.
• 2. Heterogeneous ( receiver buffers, network bandwidth and delay ).
• 3. Fairness in bandwidth consumption of competing flows.
• 4. Efficiency in utilization.
• 5. Congestion control ( that effectively avoids situations of congestive collapse ).

            Transmission Control Protocol (TCP) is a means for building a reliable communications stream on top of the unreliable packet Internet Protocol (IP). TCP is the protocol that supports nearly all Internet applications. The combination of TCP and IP is referred to as TCP/IP and many people imagine, incorrectly, that TCP/IP is a single protocol.

Performance Metrics of TCP  :

Goodput :

 This is the measure of how efficiently a connection utilizes the network. It is determined as the ratio of useful data received at the destination and the total amount of data transmitted by the source. If a connection requires a lot of extra packets to traverse the network due to retransmission, its goodput is low. It is desirable that each connection have as high a goodput as possible. Clearly, this metric is of great significance for efficient operation of a network.

Throughput :

 This is the measure of how soon an end user is able to receive data. It is determined as the ratio of the total data received by the end user and the connection time. A higher throughput will directly impact the user’s perception of the quality of service.

Article Source:http://www.articlesbase.com/networks-articles/transmission-control-protocol-tcp-789291.html

The first way you can do this is, of course, to apply such a certificate from a trusted Certificate Authority (CA), such as VeriSign. But can you do this without a CA?

Yes, it is possible for you to generate such a certificate manually using open source software. However, note that the certificate is self-signed, meaning it is signed by you as the trusted root source.

To do this, you have first to download a piece of software than can generate PCKS12 format certificates. The most common one is OpenSSL software.  You can visit this website to know more:

http://www.openssl.org.

The original OpenSSL software is made primarily to be run on the Linux platform. As a general Windows user, you might need to use the program on a Windows platform, and may not know how to compile the source code of OpenSSL to make it run on a Windows platform. If you have this headache, you can try the Windows compatible OpenSSL work available for free here:

http://www.slproweb.com/products/Win32OpenSSL.html

Upon successful installation of the software, go to the bin directory of your installation to locate the software openssl.exe that you need to use to generate PKCS12 certificate.

I followed the instructions here to create my own certificate:

http://tinyurl.com/4s5zqo

I have added my own explanations and remarks and simplified a bit the process. Here are the steps:

Assume you have installed your software on the path c:\Openssl

1.    Generate a RSA Private Key in PEM format

Type:
>C:\Openssl\bin\openssl.exe genrsa -out my_key.key 2048
Where:

• my_key.key  is the desired filename for the private key file
• 2048  is the desired key length of either 1024, 2048, or 4096

2.    Generate a Certificate Signing Request:
Type:
>C:\Openssl\bin\openssl.exe req –new –key my_key.key –out my_request.csr

• my_key.key is the input filename of the previously generated private key
• my_request.csr  is the output filename of the certificate signing request

3.    Follow the on-screen prompts for the required certificate request information.
4.    Generate a self-signed public certificate based on the request.
Type:
>C:\Openssl\bin\openssl.exe x509 -req -days 3650 -in my_request.csr -signkey my_key.key -out my_cert.crt

my_request.csr  is the input filename of the certificate signing request
my_key.key is the input filename of the previously generated private key
my_cert.crt  is the output filename of the public certificate
3650 are the duration of validity of the certificate. In this case, it is 10 years (10 x 365 days)
x509 is the X.509 Certificate Standard that we normally use in S/MIME communication

This essentially signs your own public certificate with your own private key. In this process, you are now acting as the CA yourself!
5.    Generate a PKCS#12 file:
type:
>C:\Openssl\bin\openssl.exe pkcs12 -keypbe PBE-SHA1-3DES -certpbe PBE-SHA1-3DES -export -in my_cert.crt -inkey my_key.key -out my_pkcs12.pfx -name “my-name”

• my_cert.crt  is the input filename of the public certificate, in PEM format
• my_key.key  is the input filename of the private key
• my_pkcs12.pfx  is the output filename of the pkcs#12 format file
• my-name  is the desired name that will sometimes be displayed in user interfaces.

6.    (Optional) You can delete the certificate signing request (.csr) file and the private key (.key) file.
7.    Now you can import your PKCS#12 file to your favorite email client, such as Microsoft Outlook or Thunderbird. You can now sign an email you send out using your own generated private key. For the public certificate (.crt) file, you can send this to others when requesting them to send an encrypted message to you.

Tags: self-signed Public Key, OpenSSL command

Originally, you can use PGP (Pretty Good Privacy) freeware to communicate freely. PGP freeware can be downloaded here:

http://www.pgpi.org/products/pgp/versions/freeware/

However, since they have recently taken down the freeware for the Windows platform, I’ll show you how to use another piece of software called “gpg4win” to do the same thing.

This software was created from an open source effort, and it supports OpenPGP standard. With a suitable plugin, you can use this with some other email clients such as Thunderbird and Clawmail for S/MIME email encryption.

You can download the latest version here:

http://www.gpg4win.org

Upon successful installation, you’ll find the following welcome screen:

Select “Generate key now” if you do not have a PGP private and public key pair.

Input your full name and email address, then carefully input a passphrase. This is an important step, so select something you can recall because you need to correctly enter your passphrase when you want to use your private key later.

Follow the onscreen instructions and create your key pairs. If you require a backup key to be generated, make sure you save the key pair in a safe place.

Now you can see your newly generated key in the application windows like the one I have generated for myself:

Public Key Infrastructure: Using GPG4WIN

However, before you ask someone to send an encrypted message to you, you need to export your public key to them. You can select the “Export” function of the application window to do this.

After selecting the Export function, the program will ask you where to save the exported public key. Select a location where you can retrieve the saved public key later.

Now you can send your key to anyone who needs to send you confidential messages. Those who have your public key can then encrypt the message using your public key. Those encrypted messages can only be opened by you, who owns the private key.

As an example, suppose there is someone who already has encrypted a message (or simply a file) using your public key. Let’s call the original file “plaintext.doc,” and the encrypted file you received should be “plaintext.doc.gpg”. (The software adds the file extension “.gpg” to the output file it has encrypted)

Pressing the “Files” button under the application window displays the program’s file manager. You can locate and select the file “plaintext.doc.gpg” that has been saved in your computer previously.

GPG4WIN File Manager

By pressing the Decrypt button, you are prompted to enter the passphrase for your private key to decode the file. Upon presenting the correct key, you should now have the decrypted file under the same directory of your encrypted file.

To encrypt any file to other people, you need to import their public key by using the Import function of the main application screen. Select the public key file you obtain from other people (this should be a file with file extension “asc”), and click okay to proceed with the import.

By using the same file manager, you can select the file you want to encrypt and then choose the “Encrypt” function to produce the encrypted output file. Remember to use the public key of the person you have just imported to encrypt the file. You can then send this file to the party who owns the private key of the corresponding public key you have just imported to encrypt the file. That party should be able to decrypt the file using his/her private key.

Try this software and let me know if you have any problems or issues by leaving a message here.

Tags: GNU Privacy Assistant

The Google Browser is an open source project, and many of the components it was built on use open source software. One of them is the open-source rendering software called WebKit. This component was found to have a security flaw in its older version. It allows the attacker to maliciously trick web surfers into downloading a java (or other types of) executable file from a webpage. As the downloaded file appears, a button under the Chrome browser could be pressed by the user and hence run the program.

Since a java executable file will not warn the user before it runs, the user could accidentally trigger a malicious java program.

For details of this news, refer to this article:
http://www.cw.com.hk/article.php?id_article=2236

This security flaw has been identified previously with Safari, the browser from Apple. Apple patched the flaw last June.

To avoid the possible download of a malicious file, you can turn on the option to prompt the user for the file download path under Options → Minor Tweaks → Ask where to save each file before downloading.

In fact, other than this security issue, I always recommend using browsers under open source efforts such as Firefox, or now Chrome, because those browsers are built using program sources that are open to everyone. Then, security experts can always look at the program code details inside the program to uncover potential security flaws. This makes the software safer to use in the long run.

Tags: Google Chrome, Apple Safari, Google Chrome Security Issue, Google New Browser

A trojan horse or spyware operates by running on your computer and opening a communication port (TCP port) to communicate with the remote hacker, so he or she can “spy” on your computer. The easiest way to detect this activity is to look at the ports opened on your computer by using the built-in DOS function netstat. At the DOS prompt, type this command with the switch “-a”, (i.e. “netstat -a”) to look for the ports opened on your computer.

If you have no idea what ports are usually related to a trojan horse, you can do a search on any search engine for the term “common trojan horse ports”. Here are two of the reference sites I’ve found:

http://www.doshelp.com/Ports/Trojan_Ports.htm

http://personal.telefonica.terra.es/web/oscarmartinez/_articlesan/article49-Trojan-horse-ports.htm

If you still have a hard time decoding the lists from these reference sites, you can use a handy program called “fport”. Download this here:

http://www.foundstone.com/us/resources/proddesc/fport.htm

This program helps match your opening ports with the programs in your computer. This is easier way to locate a particular suspicious program in your computer to uncover any potential spyware residing on your computer.

Please note that since this is a command mode program, you need to bring up a command prompt window by choosing Start ==> Run and then type in the command “cmd” in the “Run” window. Next, type in the exact path of the program. For example, if you have installed the program under c:\, type in c:\fport to run it. The program will create a list of programs associated with your computer under inspection. If you have difficulty comprehending a long list of ports on the command prompt window, you can tell the program to redirect the outputs to a text file for printing and later analysis. You can do this by typing, for instance, “c:\fport > c:\output.txt” to create a file named “output.txt” on your c:\ drive.

This is a handy tool for running an inspection on your computer to detect any possible hacker’s attack. I recommend that you use it regularly – it’s to your benefit.

Tags: Trojan Horse Removal, Popular Trojan Horse Port List

The operation of Public Key Infrastructure strongly depends on “trust”.  And this is also related to the application of asymmetric cryptography technique.

To illustrate this, let’s suppose Bob wants to send a message to Mary securely over the Internet. He needs Mary’s public key to encrypt the message. Theoretically, it is Mary, who owns the one and only one private key of her own, who can decrypt the message. So Mary is the only recipient who can open this message. Bob achieves his objective of keeping the secrecy of this message and revealing it to Mary only.

But the problem is: how can Bob get Mary’s correct public key? Suppose hacker Tom wants to intercept their communication. He can create a fake public key for Mary and send it to Bob. Bob, without knowing that this key is fake, uses it to encrypt the message he intended to send to Mary. The message could then be compromised by Tom for he is the person who owns the corresponding private key to the fake public key he created for Mary.

Tom can then even further re-encrypt the secret message using Mary’s real public key, sending it to Mary, and she doesn’t realize that someone other than her has read the message. And worst of all, Tom can modify the message before he encrypts and sends it, compromising both the confidentiality and the integrity of the message.

How can Bob solve this problem? He can ask for a trusted third party to help verify Mary’s public key. Let’s say this third party is Peter. Peter can help Bob by signing on Mary public key using his own private key. However, there are two conditions that need to be satisfied for this verification to work:

• First Bob must have full faith in Peter’s role as a verifier.

• Second, Bob must have an authentic public key for Peter in his key database. He needs Peter’s public key to verify Mary’s signed public key and hence reconfirm the validity of Mary’s public key sent by Peter. (Without Peter’s authentic public key, Bob has no way to ensure he has Mary’s correct public key.)

If the above two conditions are satisfied, there is no way that hacker Tom can send a fake public key for Mary to Bob, because Bob can identify it as fake, with the help of Peter.

But then this leads to another problem: Bob must have a trusted and verified public key for Peter! This seems to create the very same problem involved with verifying Mary’s public key. Bob needs to repeat the same verification procedure used for Mary’s public key, looking for someone who can verify Peter’s public key. This problem can go on and on in a circle until Bob can find an ultimate trusted “root” of public keys.

In the modern public key infrastructure (PKI), the role of Peter is played by a so-called Certificate Authority (CA). In a communication system, CAs are trustworthy organizations that have the corresponding, verified public keys of the users you want to communicate to. The CA holds a database containing the signed public keys it issued for the users who have applied and obtained the public key/private key pair through it. The private key is kept by the user, and the public key is posted to the public and maintained by the CA.

You must have trusted CAs in your database or otherwise the above story can never reach its end.  Take our popular Internet Browser IE as an example. If you take a look at Tools ==> Internet Option ==> Content ==> Certificate ==> Trusted Root Certificate Authorities, you can see it contains a long list of trusted Root CAs.

Public Key Infrastructure: Trusted Root Certificate

The popular ones in the USA are VeriSign, Thawte, etc., which are commercial organizations. In most other regions, CAs come from Government initiatives. Take my home country of Hong Kong as an example. The official CA here is the Hong Kong Post Office, which is a governmental department, with its original function serving the postal service in Hong Kong. Government-backed organizations possess the “trust” factor, and that is an important criterion for a root Certificate Authority who needs to sign and verify its publicly issued keys.

Each CA must possess a very robust infrastructure of its Internet public key directory in serving the intended communication parties of its certificate clients.

Without CAs, you would have to verify the public key yourself. In the above case, Bob would need to verify Mary’s public key before he sends her any message encrypted by the public key he has on hand. This can be done with offline communication such as phoning Mary to verify the key, or simply getting the key from Mary by meeting her face-to-face. Of course, this is very inconvenient and impractical in most electronic communication cases.

anti spam filtering

I have been using Gmail, Yahoo! Mail, and Hotmail for very long time. My general feeling is that the super-powerful anti spam filtering capability of Gmail is unprecedented. It can eliminate almost 98% of spam emails while at the same time maintaining an almost zero error rate of filtering legitimate emails. It definitely outperforms the other two free email systems.

I am always curious how it achieves this phenomenal success rate, but I find no clue at all. Having had no success in finding its algorithm, I turn to a very practical question: How we can make use of its powerful anti spam filtering capability to handle our daily corporate email reception task?

The first solution is to use Gmail for receiving emails from your contacts. That sounds easy and straightforward, but the downside is that you have to give up the corporate email address that signifies your corporate identity. How can we preserve that?

Here is a quick solution you can try. Since Gmail allows email received to be forwarded to another email address, you can follow these steps to set this up.

First, you’ll need to create the following three email addresses for each staff member of your company:

1. The primary corporate e-mail, which is shared with contacts. Say, for John Doe of your company XYZ Inc., you can john.doe@xyz.com.
2. A second corporate e-mail, called john.doe_filtered@xyz.com. (You’ll see the use of this second e-mail in a few minutes.)
3. A Gmail account, with an address similar to: john.doe-xyz@gmail.com

Next, configure the first, primary email address to forward email to the Gmail address.

In the Gmail account settings for the Gmail email address, select the option “Forwarding and POP/IMAP” as shown below:

You will see the following screen:

anti spam filtering setup - Step 2

Set this to forward to the second corporate email address of your staff (i.e., the john.doe_filtered@xyz.com address, as shown in the above screen capture).

Now John Doe can configure his email client to read spam filtered email from the second email account. Those emails are originally addressed to his primary email address, filtered by Gmail, then automatically forwarded to his second corporate email account.

What John needs to remember is to make sure the email address john-doe_filtered@xyz.com is hidden from his contacts. He only uses it as a tool to receive the filtered emails.

If you really want to own the Gmail account as a private labeling service to your company (and that entitles you to own the big storage space of Gmail for each of your private corporate email account and also the spam filtering service), you can register for a private label email program through Google Apps here:
http://www.google.com/a/help/intl/en/index.html

However, this involves pointing all your corporate emails to Google’s Server for storage and processing. I am not so sure if this is a good idea for your company, although this service is basically free with an option to pay a small fee to receive technical support service.

Essentially, the hackers use Google to hunt for sites with a problem in the web server program codes and exploit them using the knowledge gained from the error messages displayed on the problem websites. In this particular case, the hackers used the SQL command to take control of the sites under attack.

(If you are interested to know about how to work safely using SQL commands, read our post about Buffer Overflow Attack here: http://www.bestinternetsecurity.net/52.)

Some security experts attribute this situation to the usage of Microsoft-related technologies in web sites, such as Microsoft’s own Internet Information Servers (IIS) and its SQL server.

“Whitehat Security’s Grossman speculates that machines running that software were targeted because they allow several commands to be injected in a single user input field on the sites they host, making those sites easier to hijack,” according to Forbes News.

However, I have a different view, and this is the same comment that I expressed in my previous post: It does not matter what technologies you are using to run your websites. What does matter is taking extra care in writing programs that use SQL commands to manage program data. If in the original program design you fail to carefully validate users’ inputs, you will open doors to possible attacks. This is especially disastrous if you fail to do so with web application programming, like in the case we are discussing now.

But as I have also said, it is extremely difficult (if not totally impossible) to write completely bullet-proof code. But to be aware of what can happen if you do not take extra steps to write code that carefully lessens the risk of attack is more than half of the battle. Read the news in the reference section to know more about this case.

Reference:

¹Greenberg, A. (2008), Google-Hacking Goes To China, Forbes.com LLC, Available from: http://www.forbes.com/2008/04/28/hackers-google-china-tech-security
-cx_ag_0428hack.html?partner=yahootix [Accessed 28 April 2008]

Tags: SQL Programming, Application Security, Google Hacking, Buffer Overflow Attack