Tech-support scams, in which fraudsters pose as computer technicians who charge hefty fees to fix non-existent malware infections, have been a nuisance for years. A relatively new one targeting Dell computer owners is notable because the criminals behind it use private customer details to trick their marks into thinking the calls come from authorized Dell personnel.

"What made the calls interesting was that they had all the information about my computer; model number, serial number, and notably the last item I had called Dell technical support about (my optical drive)," Ars reader Joseph B. wrote in an e-mail. "That they knew about my optical drive call from several months prior made me think there was some sort of information breach versus just my computer being compromised."

He isn't the only Dell customer reporting such an experience. In a Dell forum post from July, Ars reader Patrick Z. reported receiving similar calls. When he pressed company representatives to explain how the scammers had so much information about him, a company employee shut him down. "Dell is aware of this and other complaints and is investigating," the employee wrote. "No, there will not be a public post/blog. We consider this closed from a Forum perspective."

What's more, a blog post published Tuesday reported scammers knew of every problem the author had ever called Dell about. None of those problems were ever discussed in public forums, leading the author to share the suspicion that proprietary Dell data had somehow been breached.

The blog post went on to detail several posts on Dell's public support forum reporting the same phenomenon. In all, there were eight separate customers. In addition to having the customers' phone numbers, model numbers, and serial numbers, the scammers in some cases also knew of previous support calls the targets had made.

"Was DELL hacked...?? How did this 'helpful tech representative' have my contact info AND knowledge of my technical issue ???????" one person posting on Dell's website in July asked. "DELL??? HELLO ????"

Six months later, Dell still hasn't answered. In a series of e-mail exchanges, Ars repeatedly asked Dell representatives if they had any reason to suspect the scammers hacked or otherwise breached Dell security to obtain the customer data. The representative acknowledged the ongoing scam and pointed to this advisory Dell officials issued in October. Among other things, the advisory requests anyone who receives such a call to report it using a link on Dell's website.

"Protection of our customers' data is a top priority for Dell," the spokeswoman wrote. "We ask our customers keep in mind, we do not make unsolicited calls asking to charge to fix an issue they did not report or previously request help with unless they have signed up for our premium support services like Dell Tech Concierge, Dell Premium Support or Dell ProSupport services."

The spokeswoman, however, didn't answer the question Ars asked repeatedly—did Dell officials have any reason to believe its customer data had been compromised, and if not, how did they believe the scammers had access to serial numbers, contact information, and past support calls?

One theory that partially answers the question is that the scammers exploited a vulnerability that became public in November . It resided on Dell PCs that came pre-installed with digital certificates that made it easy for attackers to cryptographically impersonate any website on the Internet . The same certificate, it turned out, also allowed hackers to surreptitiously obtain the unique service tag Dell assigns to computers it sells.

The theory still doesn't explain how scammers obtained contact information and support histories. The vulnerability, however, does demonstrate the plausibility that hackers could have devised a way to obtain personal details belonging to Dell customers. For the time being, owners of Dell computers should presume their support histories and purchase and contact information has been compromised, and act accordingly.

Post updated to add details about Patrick D.