Does a computer with backdoors have to be reformatted?

[Thetech]

Is it true that once a computer is infected with backdoors there's no point in cleaning it?
It seems kind of silly to me, because who's to say that a computer doesn't have a backdoor to begin with. More than likely my thinking is flawed though.

 

[Chiefcrowe]

No, not if you are confident you were thorough and removed everything.

The safest bet is to reformat it though.

 

[Red Squirrel]

I just format. I could spend hours if days to sift through all of it to try and clean it manually, but I find it's faster to just reformat and it's 100% that it will be gone. Usually what I do is a scan to let various malware tools do their job, then I check it and look for anything suspicious, if it looks safe I leave it, if it's still fishy I don't spend more time on it and just format.

 

[Nocturnal]

Depend on what type of computer this is. If it's a business computer with critical data that could lead to a severe security breach, I'd definitely consider formatting. You never now these days, antiviruses are not perfect and even with the help of ComboFix, SDFix, HiJackThis, MalwareBytes, and even help from forums, you can never be 100% certain that you've removed everything.

It's unfortunate but that's the nature of this stuff.

 

[Thetech]

Originally posted by: Nocturnal
Depend on what type of computer this is. If it's a business computer with critical data that could lead to a severe security breach, I'd definitely consider formatting. You never now these days, antiviruses are not perfect and even with the help of ComboFix, SDFix, HiJackThis, MalwareBytes, and even help from forums, you can never be 100% certain that you've removed everything.

It's unfortunate but that's the nature of this stuff.

Makes sense. Would it be safe to back any of the files up before reformatting? From what I've read there is a chance that files could contain a backdoor. But wouldn't something like that be obvious? I mean there's no reason for a word document to have 2 pages of text and be 50MB large.

 

[n0cmonkey]

Originally posted by: Thetech

Originally posted by: Nocturnal
Depend on what type of computer this is. If it's a business computer with critical data that could lead to a severe security breach, I'd definitely consider formatting. You never now these days, antiviruses are not perfect and even with the help of ComboFix, SDFix, HiJackThis, MalwareBytes, and even help from forums, you can never be 100% certain that you've removed everything.

It's unfortunate but that's the nature of this stuff.

Makes sense. Would it be safe to back any of the files up before reformatting? From what I've read there is a chance that files could contain a backdoor. But wouldn't something like that be obvious? I mean there's no reason for a word document to have 2 pages of text and be 50MB large.

That's assuming the backdoor is that big. These things can get tiny.

Safest bet is to reformat and restore files from KNOWN GOOD backups. Knowing those backups are good is the tricky part.