Trojans and Firewall

Trojans

(1) Information
These are computer programs that can hide themselves behind an innocent looking e-mail attachment (e.g. a tempting computer game). Once the attachment is executed, this form of virus called trojan will install itself into the computer and it can now start doing damage to your computer. Immediate protection is to install a Personal Firewall and an Virus Protection program.

Some trojans has spyware, which is software that keeps track of Internet usage statistics and it will send these information back to the creator.

The serious ones (e.g. Back Orifice, Sub Seven) are able to allow the creator/attacker to gain remote control of your computer. This means the attacker can virtually do anything as if he/she is sitting in front of your computer. The attacker can explore your directories, files and retrieve information that is useful to the attacker. The is a security threat that is very damaging.

Here is an interesting article on rogue dialers. A dangerous trojan.

Preventive measure against trojans

Say you receive an e-mail attachment. If you notice that it is not from a reliable source, please do not open it. Period.

Firewall

Normally an anti virus program comes with trojans detector and cleaner. For a better secure protection it is prudent to install a personal firewall. A firewall is a security device that sits in between your PC and the Internet. Any application that wants to connect to your PC need to pass through the firewall. Firewall is able to block unauthorized network traffic from the Internet to enter your PC when configured properly. You can customized the rules of the firewall to allow only Web (HTTP) and Secure Web (HTTPs).

A personal firewall or small business firewall is a small scale firewall that protects individual PC/small peer-to-peer network of PCs. Larger firewalls (e.g. Checkpoint, PIX) protects the entire corporate network where there can be hundreds or thousands PCs.

This is especially true for notebook users. If they are in the office, the office firewall will protect them from Internet nasties but once out of the office (hotel, home), the notebooks are opened to attacks. So it is better get the notebooks protected with personal firewalls if you are constantly travelling and online via hotel/cafe broadband services.

Another method is cleaning the temporary internet files on a computer, or finding the file and deleting it manually. Normally, anti-virus software is able to detect and remove the trojan automatically. Or else, Reboot the computer in Safemode and run an Anti-Virus to detect and clean the trojan. Please refer to site on spyware removal, anti virus protection to download the virus scan and spyware blockers.

So the lesson learned is to install a personal firewall and get the rules working for you. It will do you good.

 

How to test if your firewall is configured to protect your PC.

TEST Action. I used a port scanner with latest vulnerability updates and scanned/dos this PC with the firewall installed. It did its job of denying the scanner. This just demonstrate the importance of a firewall as the basic defence.