Symantec has updated its anti-virus definition files after a duff update falsely identified two open source packages as adware.

Norton Anti-Virus updates issued on Sunday falsely detected both Filezilla, open source FTP client, and NASA World Wind, an open source virtual globe developed by NASA and others, as the parasitic program Adware-Cpush. An update issued on Monday fixed the problem.

False positives are well known as something of an Achilles heel for signature-based malware detection. Problems crop up regularly.

As the SANS Intitute's Internet Storm Centre notes, the pressure on anti-virus vendors to release signature updates quickly is growing. Inevitably, this means testing, particularly against more unusual software packages, becomes (at best) perfunctory.

If VXers exploited this behaviour it might be possible to create strains of malware that matched the signature of "safe" files. "Manipulating malware to maximise false-positives could be an entertaining (and certainly painful) way to wreak havoc. Some basic research exists on this theory already, though nothing ready for market," SANS researcher John Bambenek writes. ®