First reported by Brian Krebs (as usual), security vendor Bit9 was compromised and used to infect their customers.

But earlier today, Bit9 told a source for KrebsOnSecurity that their corporate networks had been breached by a cyberattack. According to the source, Bit9 said they’d received reports that some customers had discovered malware inside of their own Bit9-protected networks, malware that was digitally signed by Bit9’s own encryption keys.

They posted more details on their site after notifying customers:

In brief, here is what happened. Due to an operational oversight within Bit9, we failed to install our own product on a handful of computers within our network. As a result, a malicious third party was able to illegally gain temporary access to one of our digital code-signing certificates that they then used to illegitimately sign malware. There is no indication that this was the result of an issue with our product. Our investigation also shows that our product was not compromised.

We simply did not follow the best practices we recommend to our customers by making certain our product was on all physical and virtual machines within Bit9.

Our investigation indicates that only three customers were affected by the illegitimately signed malware. We are continuing to monitor the situation. While this is an incredibly small portion of our overall customer base, even a single customer being affected is clearly too many.

No sh**.

Bit9 is a whitelisting product. This sure is one way to get around it, especially since customers cannot block Bit9 signed binaries even if they want to (well, not using Bit9, at least). This could mean the attackers had good knowledge of the Bit9 product and then used the signed malware to only attack Bit9 customers. The scary part of this? Attackers were able to enumerate who was using Bit9 and target them. But this kind of tool should be hard to discover running in the first place, unless you are already in the front door. This enumeration could have been either before or after the attack on Bit9, and that’s a heck of an interesting question we probably won’t ever an answer to.

This smells very similar to the Adobe code signing compromise back in September, except that was clearly far less targeted.

Every security product adds to the attack surface. Every security vendor is now an extended attack surface for all their clients. This has happened before, and I suspect will only grow, as Jeremiah Grossman explained so well.

All the security vendors now relishing the fall of a rival should instead poop their pants and check their own networks.

Oh, and courtesy our very own Gattaca, let’s not forget this.