A Look at the Buffer-Overflow Hack

The fact that an application is used all over the Web does not mean it is secure, so take care when installing a new application on your machine. In fact, WWW applications are more likely to be searched deeply for security holes by crackers with bad intent. System administrators should read the security newsgroup and related web pages in order to keep applications known to have security holes off the system and to upgrade them when patches become available. Application programmers should take care to write tight code containing proper checks for array and variable lengths in order to foil this type of hack.

Finally, I would like to briefly mention three other things. One, a kernel patch is available that makes the stack memory area a non-executable one. I have never tested it, since applications do exist which count on the fact that the stack is executable, and these applications will most likely have problems with this patched kernel. Two, a special mode to the Intel processor is available that has the stack grow from the lower memory addresses to the higher memory addresses, thus making a buffer overflow almost impossible. Three, a set of libraries available on some systems helps the programmer write code with no such errors. All the programmer has to do is tell the library functions the assumptions about a variable and these functions will verify that the variable meets the specified criteria.