Between three to five per cent of corporate systems are infected by bots, according to a study by security firm Damballa.

The finding comes from Damballa itself and is being used to promote the need for its line of security appliances, designed to block communications between infected hosts and zombie-control servers, as an added layer of protection in addition to conventional anti-virus defences. Self-interest aside, the Damballa study may point to shortcomings in conventional anti-virus software that are well worth considering.

A study (pdf) of antivirus scanning tools by Damballa over the last six months found that only 53 per cent of 200,000 malware samples were detected by conventional scanners on the day they first appeared. Around one in seven (15 per cent) of the sample were undetected even after 180 days.

Damballa reckons the average gap between malware release and detection using conventional antivirus is 54 days. ®