Fighting malware and spam

Cavity filler

Virus that fills empty space in files

A cavity filler is a type of file-infecting virus which seeks out unused space within the files it infects, inserting its code into these gaps to avoid changing the size of the file and thus not alerting integrity-checking software to its presence.

CIH, aka the Chernobyl virus, is a notable example of this technique.

Poll

Malware Prevalence

NetSky
Agent
Zbot
Bifrose/Pakes
Mytob