Internet security firms in the Republic were flooded with calls yesterday as the latest computer virus swept through corporate e-mail systems.

Dun Laoghaire firm Priority Data Systems received at least 30 calls yesterday and advised some firms to shut down e-mail systems to avoid contamination.

The Sircam virus is particularly troublesome because it arrives with random subject lines and attachment names, meaning there is no easy way to warn computer users. The computer worm can expose sensitive data creating a list of files with extensions such as .DOC, .ZIP and .JPG that are in the victim's My Documents folder. The virus then sends copies of itself to users in the victim's address book, including one of those files chosen at random.