Is your computer clean? Is it really?
Posted: June 11, 2004, 5:55 pm
I can say with some certainty that if you have a high-speed Internet connection and your PC is connected directly to the Internet with no hardware or software firewall, you are very likely infected with a virus. I would highly recommend purchasing a hardware firewall, and if you're really concerned, getting a software firewall. Generally speaking the hardware firewalls require minimum configuration on your part, and will protect you from most attacks.
A few of the newer viruses, specifically Phatbot, Agobot, and Gaobot (though I'm sure others do this as well) will actually disable your antivirus software, personal firewall (not a hardware one), regedit, and several other pieces of software on your computer. Since a lot of times when a virus first comes out, the definitions aren't yet in the antivirus software, you can be completely up to date on your virus definitions, and still be infected with whatever the newest virus is.
These viruses spread by sending out frames from your computer to other computers. Basically they scan remote IP addresses looking for machines that are vulnerable, and if they find one, they infect the remote machine and further spread.
So the question is, if your virus software can't detect a virus, how do you know if your PC is TRULY clean? The answer my friends is a network packet sniffer. A network sniffer will allow you to see the frames being sent out from your computer. If you're sending out traffic you can't explain, chances are you have a virus.
Anyway, let me cut to the chase.... There's a free network sniffer available for download at http://www.ethereal.com. It works with all 5 NICs, 2 of which are wireless, that I have on my different computers, and it will show the output of a sniffer capture in realtime, so you can see frames as they go out. It has a whole shitload of filters you can apply, as well as color coding the frame etc. I use it daily at my job, but given the free cost, it's a good way to see what traffic your computer is sending out. If you're computer has no web applications running, it should be relatively quiet on the network except for the occasional NETBIOS frames. If anyone's interested in help setting this up, or advice on how to use it to see if their PC is really clean, let me know and I'll do my best.
A few of the newer viruses, specifically Phatbot, Agobot, and Gaobot (though I'm sure others do this as well) will actually disable your antivirus software, personal firewall (not a hardware one), regedit, and several other pieces of software on your computer. Since a lot of times when a virus first comes out, the definitions aren't yet in the antivirus software, you can be completely up to date on your virus definitions, and still be infected with whatever the newest virus is.
These viruses spread by sending out frames from your computer to other computers. Basically they scan remote IP addresses looking for machines that are vulnerable, and if they find one, they infect the remote machine and further spread.
So the question is, if your virus software can't detect a virus, how do you know if your PC is TRULY clean? The answer my friends is a network packet sniffer. A network sniffer will allow you to see the frames being sent out from your computer. If you're sending out traffic you can't explain, chances are you have a virus.
Anyway, let me cut to the chase.... There's a free network sniffer available for download at http://www.ethereal.com. It works with all 5 NICs, 2 of which are wireless, that I have on my different computers, and it will show the output of a sniffer capture in realtime, so you can see frames as they go out. It has a whole shitload of filters you can apply, as well as color coding the frame etc. I use it daily at my job, but given the free cost, it's a good way to see what traffic your computer is sending out. If you're computer has no web applications running, it should be relatively quiet on the network except for the occasional NETBIOS frames. If anyone's interested in help setting this up, or advice on how to use it to see if their PC is really clean, let me know and I'll do my best.