SOFTWARE security firms warned computer users on Friday to guard against a new, more virulent strain of the “Love Bug” virus that swept the world earlier this month. Experts said several thousand computers were already infected by new e-mail virus, dubbed “Herbie: Love Bug II”. It causes more severe damage than the original becauses it wipes files clean and tries to hide by changing its appearance. But there are hopes it may not spread as widely because companies have updated security since the first Love Bug. Simon Perry, vice president of security solutions at US-based Computer Associates said the virus renamed all files on a computer’s local hard drive and associated network drives with a VBS (visual basic script) extension and set the file size to zero — effectively making the computer system and network inoperable.