Two security firms Friday issued new warnings about two separate threats affecting Microsoft products.Two security firms Friday issued new warnings about two separate threats affecting Microsoft \u00a0products.Sophos\u00a0reported evidence of new malware planted on Web sites that exploits a previously announced -- and as-yet-unpatched -- Internet Explorer security vulnerability. The Clunky-B Trojan horse allows hackers to install and run malicious software on users' machines when they visit sites containing the malware, said Graham Cluley, a senior technology consultant at Sophos.The code is only the latest of several Trojan horses seeking to exploit an Internet Explorer vulnerability that Microsoft first disclosed in May. At that time, the flaw wasn't considered very serious because it was believed that hackers who exploited it would only be able to shut browsers down while causing little other damage, Cluley said.The recent emergence of Trojan horses targeting the flaw, however, prompted Microsoft to issue an advisory last week. That advisory was updated on Tuesday to inform users that it was aware of the proof-of-concept code and is investigating the matter."Upon completion of this investigation, Microsoft will take the appropriate action to help protect our customers. This may include providing a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs," the company said in that advisory. Microsoft's next security update is due on Dec. 13.For the moment, at least, there is little evidence that the Trojan horse code poses a major threat to most Internet users, Cluley said. The only users likely to get infected are those who visit pornographic sites. But it's possible that hackers could soon start planting the malware on other sites they may have compromised, he said.Until a fix is available from Microsoft, users should consider changing the configuration of Internet Explorer to turn off or prompt before allowing Active Scripting to run, Sophos said in its advisory.Meanwhile, a separate security advisory came from database security vendor Imperva Inc., which warned users of a vulnerability it discovered in Microsoft's SQL Sever 2000 database that allows potential attackers to mask their log-in names from the software's audit tools.Users who take advantage of the flaw could gain access to a vulnerable database and take any action they want without fear of their actions being audited, Imperva CEO Shlomo Kramer said.Microsoft issued an advisory informing users of the problem on Wednesday in which it tells users how to detect the problem and work around it.