I recall one persistently nasty one that would replicate itself from two innocent-looking text files over the course of 4 reboots of the PC. It's been a few years and I can't remember the name of the variant, but the two text files (once found) proved to be its Achilles heel.As an aside, if malware appears to persistently return, even though you've removed all traces of it on the system, you need to consider that it may have copied itself to the MBR and is restoring itself upon boot. The only way to get rid of that is to re-write the MBR or do a full format (which will obviously re-write the MBR then).
It also involved a bunch of registry work, too.
Sure, there are lots of tricks like that to employ that most people are not aware of. As terrible as some of those things are, you just sometimes have to appreciate the ingenuity and cleverness of them. Often these tricks are only discovered by forensic examination of the system offline to perform analysis of the temporal locality of the malware files being executed.
My Computer
At a glance
XP / Win7 x64 ProIntel Quad-Core Q9450 @ 3.2GHz2x2GB GSkill DDR2NVIDIA GeForce 8600 GTS (EVGA)
- OS
- XP / Win7 x64 Pro
- CPU
- Intel Quad-Core Q9450 @ 3.2GHz
- Motherboard
- Asus P5-E
- Memory
- 2x2GB GSkill DDR2
- Graphics Card(s)
- NVIDIA GeForce 8600 GTS (EVGA)
- Monitor(s) Displays
- Dell 2408WFP
- Screen Resolution
- 1920x1200