Symantec's leading antivirus software, which protects some of the world's largest corporations and U.S. government agencies, suffers from <A HREF="http://www.cnn.com/2006/TECH/internet/05/25/antivirus.flaw.ap/index.html">a flaw that lets hackers seize control</A> of computers to steal sensitive data, delete files or implant malicious programs, researchers said Thursday. Symantec said it was investigating the issue but could not immediately corroborate the vulnerability.