Updated Four months ago Gibson Security, a group of freelance vulnerability researchers, notified Snapchat that it had found serious flaws in the image-flinging service's security and privacy systems.
Having heard nothing back, the group has now released the details and some exploit code to back up its claims.
"Given that it's been around four months since our last Snapchat release, we figured we'd do a refresher on the latest version, and see which of the released exploits had been fixed (full disclosure: none of them)," said the group in a Christmas Eve missive to the security community.
Gibson studied Snapchat's Android app, and claims to have found flaws in its private API – the interface between the software and the Snapchat servers – that enable an attacker to decode and decrypt received data, and build a database linking users to their cell numbers.
It appears photos sent via Snapchat are encrypted using AES and a key hardwired into the application's code, allowing anyone to decrypt and view intercepted images. Separately, denial-of-service attacks are also possible, we're told.
"We were able to crunch through 10 thousand phone numbers (an entire sub-range in the American number format (XXX) YYY-ZZZZ - we did the Zs) in approximately 7 minutes on a gigabit line on a virtual server," the report states.
"Given some asynchronous optimizations, we believe that you could potentially crunch through that many in as little as a minute and a half (or, as a worst case, two minutes). This means you'd be railing through as many as 6666 phone numbers a minute (or, in our worst case, 5000!)"
The published exploit code can harvest these phone numbers, and a separate piece can register multiple bogus accounts for spamming purposes, we're told.
Snapchat's application allows its predominantly young users base to send up to ten second views of pictures before they are permanently deleted. Given the current fad for sexting, and the ensuing moral panic it has inspired, the service has a significant following among those who wish to send titillating titbits to a paramour.
This crucial young adult market has had VCs valuing the firm at $800m in June, although Evan Spiegel, Snapchat’s 23-year-old co-founder and CEO reportedly turned down a $3bn offer from Facebook and $4bn counter-bid from Chinese e-commerce conglomerate Tencent Holdings.
Snapchat's audience might be young and valuable, but they are also fickle, and if malware can use the newly released information then those kinds of valuation figures may evaporate like summer mist. ®
Updated to add
Snapchat has downplayed the significance of the reported security holes, and suggested it has checks in place to thwart a mass slurping of users' private data. On its blog today, the company stated:
This week, on Christmas Eve, a security group posted documentation for our private API. This documentation included an allegation regarding a possible attack by which one could compile a database of Snapchat usernames and phone numbers.
Theoretically, if someone were able upload a huge set of phone numbers, like every number in an area code, or every possible number in the US, they could create a database of the results and match usernames to phone numbers that way. Over the past year we’ve implemented various safeguards to make it more difficult to do. We recently added additional counter-measures and continue to make improvements to combat spam and abuse.