Santy.E worm poses threat to sites badly coded in PHP

Protecting affected sites may mean recoding them

The latest version of the Santy worm poses an elevated risk to many Web sites built using the PHP scripting language, and protection of those sites may involve individually recoding them, security experts warned over the weekend.

Early versions of the Santy worm exploited a specific bug in a bulletin-board software package called phpBB, and their attacks could be prevented by applying a patch to the software (see story). However, the security flaw exploited by newer versions of the worm such as Santy.C or Santy.E is more general, and can occur anywhere a site designer has left the door open for the inclusion of arbitrary files into PHP scripts, experts at K-OTik Security in Montpellier, France, warned.

Santy.C and Santy.E behave so differently from Santy.A that K-OTik is renaming the worm PhpInclude.Worm in its advisories, the company said yesterday. The worm doesn't exploit the vulnerabilities in phpBB targeted by its predecessor, instead aiming for a wider range of common programming errors in PHP Web pages. It uses search engines including Google, Yahoo and AOL to identify exploitable Web pages written in PHP that use the functions "include()" and "require()" in an insecure manner, K-OTik said.

These functions can be used to embed the contents of a file in a Web page. If the site designer used them without sufficient checking of the parameters passed to the function, then an attacker could exploit them to incorporate an arbitrary file in the Web page, rather than the limited range presumably intended by the site designer. From there, depending on the configuration of the Web server, the attacker could move on to take control of the entire machine, K-OTik warned.

To prevent these attacks, it may be necessary to recode the site to use the include() and require() functions in a safe manner.

Eliminating the security flaws exploited by the newer versions of Santy involves no new tricks, and is simply a matter of applying long-known sound programming principles.

Copyright © 2004 IDG Communications, Inc.

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