'Knowing me, your PC, knowing you, a virus: Yaha!'Anti-virus firm Sophos is warning against a new worm on the loose wreaking havoc on European computers. Called Yaha the worm arrives as an email attachment with a variety of subject lines, many related to friendship or love. Anti-virus firm MessageLabs rates the worm as the seventh most prolific worm in the last 24 hours. Sophos urged users to update their anti-virus software.