IE 4 beta bug risks hard disks 
By Alex Lash
September 5, 1997, 4:10 p.m. PT 

                A flaw in Microsoft's (MSFT) Internet Explorer 4.0
                beta 2 puts users of the browser at risk of file
                corruption on their hard drives. 

                Discovered by a Massachusetts Institute of
                Technology alumnus with a bug-catching history,
                the most recent flaw lets a malicious Webmaster
                build a Java applet that can erase or corrupt files on
                a Windows machine. Users must visit the site where
                the applet lives. Unless the person is running a
                Java-monitoring program, the applet could be
                undetectable and launch itself automatically,
                working behind the scenes to destroy the user's
                files. 

                The problem is not due to Java itself but to
                Microsoft's implementation of Java in its latest beta
                browser. The bug also affects IE 3.0 but only when
                that browser is used with the beta version of
                Microsoft's Java software development kit 2.0.
                Macintosh users are not affected. 

                Microsoft knows about the bug and will fix it in the
                final version of IE 4.0 and in the final version of the
                Java SDK 2.0, according to product manager
                Kevin Unangst. IE 4.0 is due September 30; the
                new Java SDK is due in the same time frame.
                Meanwhile, the company has posted more
                information on its IE security Web site. 

                To corrupt a file, malicious applet writers need to
                know the exact name and location of the targeted
                file, but the paths of many Windows system
                files--autoexec.bat, for example--are easy to guess.

                "This would effectively wipe out your hard drive,"
                said Timothy Macinta, a Java consultant who as an
                MIT undergrad helped uncover an Internet
                Explorer bug earlier this year. "You could take out
                someone's system files or take up hard drive space
                by writing as many files as you can." 

                The bug only works with a combination of Java and
                DirectX, Microsoft's set of programming interfaces
                that help developers build games and other
                multimedia applications. The Java security model
                normally prevents applets from writing information
                on the user's hard drive. But a certain DirectX piece
                of code, when built into a Java applet, bypasses
                Microsoft's version of the Java security model. If
                the applet writer points the code to a specific file, it
                will add the code to the file and corrupt it. 

                The bug cannot add viruses to a hard drive nor will
                it let the malicious programmer view or steal files
                from the hard drive.