Users of Symantec antivirus software should beware. Various reports say that a researcher by the name of Alex Wheeler has identified a way for malware--malicious software--to gain entry to a computer. The vulnerability could affect a large number of Symantec software aimed both at businesses and consumers. Small businesses could be particularly vulnerable because they are more likely than enterprises to rely on both classes of antivirus software. The flaw, which attacks an open source software component of the software, could give the hacker control over the PC, the reports say.