The Associated Press reports that Symantec Corp. has fixed a major problem with its leading antivirus software that would let hackers, steal, alter data, or implant malicious programs. The antivirus software protects some of the world’s largest corporations and government agencies. Symantec began working on the patch over the Memorial Day holiday, after the problem was discovered. While there have not been detected instances of hackers exploiting the flaw, the quick turnaround from discovery to patch is indicative of the seriousness of the threat. The patch is available using the company’s “LiveUpdate” technology…