Security researchers inspecting Micosoft's Windows XP Service Pack 2 found two software flaws that could allow virus writers and malicious hackers to sidestep new security features.
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German internet security portal Heise Security published a security bulletin dated 13 August which described two holes in SP2. It also warned users about running programs from untrusted internet sites.
The flaws could allow virus writers to circumvent the security feature and write worms that spread on XP SP2 systems, according to the bulletin. However, the researcher who discovered the holes said he does not consider the flaws to be serious and he still recommended installing SP2.
Microsoft is investigating reports of a method to bypass the attachment execution services in Windows XP SP2, but was not aware of any way an attacker could use the flaws reported by Heise to gain access to a Windows machine, a spokeswoman said.
Heise security editor and chief Jürgen Schmidt and his colleagues discovered holes in an XP SP2 feature that marks files downloaded from the internet or saved from e-mails with a ZoneID.
The ZoneID records the Internet Explorer security zone from which the file originated. Internet Explorer security zones assign different levels of security permission to different sources of files and data. For example, websites and files downloaded from the internet are considered less secure than those obtained from the local area network the computer is connected to, or from the local computer hard drive.
XP SP2 saves ZoneIDs in a text file on the local computer. That file is linked to the downloaded file and is used to issue pop-up warnings when Windows users attempt to open files from a dangerous source. However, certain Windows features allow users to open files without a warning, Heise Security found.
For example, users can open files using text commands issued through the Windows command prompt, a standard Windows feature, without being warned about the risk associated with opening the file.
A second bug exploits what Schmidt called a "programming error" in XP SP2 that fails to update the ZoneID information cached for immediate use when files are renamed. That could allow malicious hackers or viruses to get around the user warnings, at least temporarily, by renaming a malicious file that would otherwise generate a warning.
Neither security hole could be exploited by a remote attacker and both require Windows users to take actions, such as opening the Windows command shell or renaming files to overwrite other files on Windows.
However, a flaw such as the failure to update cached ZoneID information could cause problems as third-party software programs try to take advantage of XP SP2.
Microsoft was informed of the holes on 12 August. The Microsoft Security Response Center said the issues were not in conflict with "the design goals of the new protections," and that it did not consider the holes serious enough to warrant a patch or workaround, Schmidt said.
A Microsoft spokesman could not confirm or deny that the company issued a statement to Heise Security.
Many security experts agree that XP SP2 improves Windows security, especially by deploying a desktop firewall by default that blocks all but common internet traffic to and from Windows XP machines. However, the hunt for holes in XP SP2 began as soon as the software update was released.
Some security researchers have predicted that hackers will discover ways to circumvent many of the XP SP2 features, even writing worms and viruses that target machines running the updated operating system.
"SP2 is not going to be the end of all viruses. Users have to be aware that the new security features of SP2 are not catch-all solutions," Schmidt said.
Microsoft encourages customers to activate the Windows XP Auto Updates feature so they can download and install Windows XP SP2 as soon as it is released to the Auto Updates service, a spokeswoman said.
The warning from Heise can be found at www.heise.de/security/artikel/50051.
Paul Roberts writes for the IDG News Service