Can Viruses/Trojans Hide From Anti-Viruses?

I was watching The Screen Savers on TechTV the other day and this guy called and said that he had something on his computer trying to do a DOS(Denial Of Service) Attack on a Korean(I think) server. he said he had ran anti-virus and stuff. They told him that they could especially if you said to download it from anti-virus and that it is going to be very hard to erase. They told him to run some more stuff and if that didn't help that they would say to re-install windows. IS this all true is it possible for it to hide from anti-viruses? Also would it be possible for a trojan on your computer and even threw scanning your computer with spyware removal tools and Anti-virus for it to still be there? I'm a newbie when it comes to viruses and stuff so if anyone could help please help me.

 

Theoretically, it's possible. I mean, polymorphism in advanced virii/trojans make it harder to detect. Most AV's have a byte "pattern" that they search for. They also search for other things in the file to "confirm" that it is the right file. With polymorphic baddies, they have no definite/set pattern that the AV's can search for. It's quite complex, but to generate "random" code sections (or random anything in fact) you need to start with something called a "seed" number. If that is known, then any random # afterwards can be predicted. Malicious code writers are also known to use multiple random seeds and various other new techniques to evade security. I hope that helps

~Nok1

 

WHOOOSHH!! Right over my head So is it possible to have a trojan and a AV nor a spyware program to pick it up? If they can hide what kind of stuff can they do while hidden? Would HiJackIt! pick it up and one of your guys be able to pick it out?

 

Usually yes...............most of the techs in here eat HijackThis logs for breakfast and it gets instinctive after a while to spot somethings not right.
If you have a quality A/V program which is regularly updated...a good firewall and your careful with what you download it makes it easier to surf with more impunity to most infections.By all means if you want you log checking out this is the best place to post it.

 

HijackThis is one program that will help us look to find crap that is needed to be removed from your system. But some of the crap is hard to find and we need to use other programs to dig them out. We just do it one step at a time. If you are still having problems then we have you run a few more programs to see if we can find them

 

There should be a program similar to SFC, but will check for "valid" files in your /system and /system32 folders... wouldn't that help a lot? *Sigh*.. if i only had the time...

 

ok let me ask this. I got a trojan called JS/Psyme almost a month ago. My anti-virus took care of it. I also posted the log and I was told I was clean. But I'm just SO worried that there is something still there. Could this be possible? I got it from just going to a website(didn't know I could get a virus that way)and I'm just so afraid it could happen again and I not know it. Would you worry about buying stuff off the net from a computer that was infected with a trojan but the Anti-Virus took care of it and the log is clean? I have a firewall but I keep hearing of viruses able to route their way threw it without you knowing. What are some programs that you guys recommend?

 

Sounds like your're in good shape, just remember to update your AV and firewall regularly . Don't worry.

oh, and keep up with all the windows updates