The hacker who posted an exploit last week that threatened a large swath of Hewlett-Packard Co.'s laptop lineup followed up Wednesday with new attack code that can "brick" nearly every HP laptop.

In a post to the milw0rm.com Web site Wednesday, a Polish security researcher who used the alias "porkythepig" spelled out a pair of vulnerabilities in an ActiveX control used by HP's Software Update, the patch management program bundled with virtually every HP- and Compaq-branded laptop.

According porkythepig's post, the Software Update bugs let an attacker corrupt Windows' kernel files, making the laptop unbootable, or with a little more effort, allow hacks that would result in a PC hijack or malware infection. In either case, a drive-by attack could be conducted by feeding users an e-mail message with a link to a malicious Web site.

"Every HP notebook machine containing the HP Software Updates application is vulnerable," claimed porkythepig. "It is possible that the vulnerable machine model list disclosed by the vendor as a confirmation to the previous issue concerning HP laptops, [the] HP Info Center case, will be similar in this case."

Last week, porkythepig disclosed multiple flaws in other software included with HP's portables. When the company patched the vulnerabilities a day later, it listed 83 affected laptops.

The scenario in which an attacker overwrites the kernel and thus "bricks" the HP or Compaq notebook, was out of the ordinary, since most hacks aim to snatch control of the machine or infect it with identity-stealing malware. But the crippling attack, said porkythepig, is actually the simpler of the two. "This attack vector doesn't require any additional victim social engineering, because the system files are always placed in the predictable locations," he said.

A drive-by attack that hopes to execute rogue code, however, requires more work. To successfully exploit the ActiveX bug in Software Update and compromise the computer, the hacker needs to know the location of certain files.

The researcher said he had tested the exploit code on Windows 2000, XP, Server 2003 and Vista, and that the vulnerabilities pose a risk to any user with either Internet Explorer 6 (IE6) or IE7 on the PC. Nor will HP be able to use the down-and-dirty fix it deployed last week, said porkythepig. After he revealed several bugs in HP's Info Center a week ago, HP issued an update that simply disabled the vulnerable software.

"Simple disabling of the vulnerable control by the vendor's patch, like in the other HP software vulnerability case, HP Info, [could still] result in the machine['s] software update system [being] compromised, and would leave the user vulnerable to future security issues," porkythepig said in the milw0rm.com write-up.

HP did not reply to e-mailed requests for confirm and comment.