An audit of 10,000 PCs in 125 corporate and public sector networks over the past nine months has found that 25.8 per cent contained pornography or other " inappropriate" images.

The sample audits by PixAlert also found that 12.4 per cent of the 12,000 email accounts monitored, and 5.4 per cent of 26,000 file server shares, were similarly affected. 

Nearly half of the images showed full nudity or sexual activity, and 0.3 per cent were determined to be illegal.

"A significant number of employees continue to ignore corporate policies and in some cases are going to extraordinary lengths to bypass protection systems in order to obtain and distribute inappropriate material," said Andy Churley, marketing director at PixAlert.

"Corporate officers wrongly assume that boundary protection systems stop all digital pornography from entering the organisation. In PixAlert's experience, almost all corporations will have a significant amount of pornography on their networks."

While 35 per cent of the inappropriate images were downloaded from the internet, 45.2 per cent were sourced from emails. Of these, 19.7 per cent were from external sources and 35.5 per cent were sent internally.

Companies are advised to enhance traditional gateway filters with network audit or real-time monitoring tools to clamp down on inappropriate material being sent internally via email.

"Companies are particularly concerned when they see the number of pornographic images being distributed by email internally or sent out to other organisations using a corporate email address," said Churley.