how to detect FUD malware?

[gh0st]

so here is my question :
how to detect FUD aka full undetectable malware?
is it better to get an AV? or can I do it manually?

[Kulverstukas]

There's a reason it's called FUD. You can always detect it manually if you know how by disassembling it, but first you have to suspect that it's actually malware - going about and analyzing all of executable would be kind of a time waste if there are many.