T-Mobile has confirmed that files posted on a full disclosure mailing list are genuine - but the company fails to explain whether or not cybercriminals really got full access to its systems, IDG reports.

Hackers published system config files from T-Mobile's US network on Saturday along with claims they had compromised the carrier's core systems. "We have everything, their databases, confidential documents, scripts and programs from their servers, [and] financial documents up to 2009," they said.

The unidentified hackers invited bids from interested parties to an email address, pwnmobile@safe-mail.net, which has since become inactive.

T-Mobile, which is investigating the hack, has issued an updated statement that the data posted matches a document on its system, but this failed to prove that customer records or other sensitive files had also been compromised:

To reaffirm, the protection of our customers' information and the security of our systems is paramount at T-Mobile. Regarding the recent claim on a Web site, we've identified the document from which information was copied, and believe possession of this alone is not enough to cause harm to our customers. We continue to investigate the matter, and have taken additional precautionary measures to further ensure our customers' information and our systems are protected. At this moment, we are unable to disclose additional information in order to protect the integrity of the investigation, but customers can be assured if there is any evidence that customer information has been compromised, we would inform those affected as quickly as possible.

Given that the hackers are attempting to attract bids for the purloined data, it's odd that they didn't publish a sample of customer records - or similarly juicy information - rather than network scans of little interest to anyone except security anoraks. A sample of data of greater interest would surely attract more interest in bidding for the information, if that was the intention.

Some security firms are beginning to conclude that the hackers are holding little beyond the network scan data already posted.

Amichai Shulman, CTO of Imperva, commented: "Rumours of a major T-Mobile data breach are all over the internet as hackers are reportedly selling confidential data to the highest bidder. Hackers have posted a list of servers they allegedly accessed and it is very comprehensive with some sensitive info in it.

“My guess is that they have been able to get access to the list of servers but not much more.”

Reports of the breach against T-Mobile US, alongside a previous confirmed leak of consumer data from parent firm Deutsche Telekom last year, detract from the firm's overall reputation in security, Shulman argued.

"Telecom operators, with the massive amounts of data they store and collect, remain prime targets. Less than three years ago, T-Mobile's owner, Deutsche Telekom, experienced a breach losing 17 million records.

"The cumulative impact of these breaches will threaten not only T-Mobile's brand image, but could also impact any telecommunications provider unless the issue of data security is vigorously addressed." ®