Because of a flaw in Microsoft's Word word processor program, documents containing macros can be modified to bypass Word's security features and make possibly devastating changes to a user's computer, the company said Friday. A macro is a small script that can be used to automate tasks, such as text formatting on a document.
The vulnerability affects Word 97, 2000, 2002, the Japanese version of Word 98 and Word for Macintosh 98 and 2001. Someone could exploit the vulnerability by performing what Microsoft calls "low-level editing" on a Word document so as to disguise the malicious macros and prevent Word's macro checker from detecting them, the company said.
Normally, upon opening a document containing macros, Word notifies users of the macros and gives users the option to run or disable them, but in this case the user wouldn't know that a malicious macro was present or that it had run. Such a macro could take any action that a user could, including changing or deleting files, contacting a Web site, disabling security settings or even reformatting a hard drive, the company said.
Users could access an affected Word document from a floppy disk, a Web page or an e-mail.
Microsoft said the bug only affects Word, but not other Office components, and that users employing the Outlook Express security update, which is included with Word 2002, would be protected from e-mail worms, and thus from a Word document with a malicious macro.
Meanwhile a new flaw was uncovered in Microsoft's Internet Information Server (IIS) versions 4 and 5 -- software used to run an estimated 6 million Web servers worldwide. the hole can let an attacker execute code of his choice on the server and is the second found in IIS this week and at least the fourth identified since the beginning of May.
This hole results from a vulnerability in a component of the Front Page Server Extensions (FPSE) which ship with IIS; Front Page is Microsoft's visual Web page builder and uses special server extensions to provide additional functionality. The component, the Visual Studio RAD (Remote Application Deployment), is an optional tool not installed by default with either FPSE or IIS and is used to help developers create software faster and easier.
The bug in the component would allow an attacker using a specially-designed packet to overflow the tool's memory buffer and run code of his choice. Normally that code would only be run in a mode that would restrict the damage it could do, but certain circumstances can let the code run in a more powerful context that make the system more vulnerable, the company said.
Microsoft does warn users that the Visual Studio RAD component should not be installed on Web servers in public use and warns users at the time of installing the component that it should be used only for internal development. The user must click past the warning in order to install the component, the company said.
Front Page Server Extensions are included in Office 2000, Office XP, Windows Server 2000, Windows Advanced Server 2000 and can be installed on Windows NT 4. The bug was discovered by Chinese security firm NSFocus Information Technology.