People using Windows computers were unprotected against new viruses for 56 days this year, research shows. Security firm Ironport counted how long it took anti-virus firms to produce an antidote following the first appearance of a malicious program. It found that, on average, anti-virus firms took 17 hours <A HREF="http://news.bbc.co.uk/1/hi/technology/4536090.stm">to respond to new threats.</A> Some viruses took far longer to tackle and in one case specific defenses took more than three weeks to appear.