Feeds

Botnet pierces Microsoft Live through audio captchas

'Look at these delineations!'

  • alert
  • submit to reddit

5 things you didn’t know about cloud backup

The prolific Pushdo spam botnet has found a new way to penetrate Microsoft's Live.com by exploiting weaknesses in the audio captchas designed to prevent automated scripts from accessing the popular email service.

A new version of the bot causes infected PCs to pull down Live.com audio captchas and return the correct response within 10 seconds, according to a researcher at anti-virus firm Webroot. The attack allows the zombie machines to send email through accounts with a Live.com address, which are whitelisted by many spam filters. The technique offers spammers an alternative to sending spam through open mail relays, which are often blacklisted.

"In one seven minute test period where I permitted the bot to operate freely, the bot demonstrated [a] remarkable capability to bypass the audio captchas," Webroot researcher Andrew Brandt wrote Monday Morning. "In most cases, it was able to submit the correct answer within two tries, though in one instance, the bot tried six times before it could proceed, and once it gave the correct answer the first time."

The attack is the latest to target captchas, the puzzles that websites use to ensure that email and forms are completed by humans rather than automated scripts. Captchas require a person to recognize a series of distorted characters that are hard for computers to read using optical character recognition programs. Audio captchas, which are available in the event the user is visually impaired, work in much the same way except that characters are verbally recited amid background static and other noise.

Over the past few years, cybercrooks have devised attacks on captchas protecting Google, Live.com, sites selling concert tickets and various other web properties. Web masters usually respond by tweaking the puzzles, forcing attackers to find new bypass techniques.

Webroot's Brandt said it's the first time he's heard of an audio captcha being targeted. It remains unclear if the attackers are sending the WAV files to sweat shops where humans then decode the audio puzzles, or if the technique works with the help of speech recognition software.

Once the captcha is solved, the botnet uses a Live.com email address to send spam with a variety of come-ons written with poor English grammar and usage. Our favorite one was "Mamma mia! your grandmother is doing so strange things here! Look at these delineations!"

The spam includes a link to a Yahoo Groups page that uses offers for free porn to coax people into giving up financial information.

A botnet primarily used to spend spam, Pushdo goes by several other names, including Cutwail, Diehard and Rabbit. Some of the IP addresses used by the audio-captcha buster have been used in the past by the Russian Business Network. Brandt's report is here. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
Ice cream headache as black hat hacks sack Dairy Queen
I scream, you scream, we all scream 'DATA BREACH'!
Goog says patch⁵⁰ your Chrome
64-bit browser loads cat vids FIFTEEN PERCENT faster!
JLaw, Kate Upton exposed in celeb nude pics hack
100 women victimised as Apple iCloud accounts reportedly popped
NIST to sysadmins: clean up your SSH mess
Too many keys, too badly managed
Scratched PC-dispatch patch patched, hatched in batch rematch
Windows security update fixed after triggering blue screens (and screams) of death
Researchers camouflage haxxor traps with fake application traffic
Honeypots sweetened to resemble actual workloads, complete with 'secure' logins
Attack flogged through shiny-clicky social media buttons
66,000 users popped by malicious Flash fudging add-on
New Snowden leak: How NSA shared 850-billion-plus metadata records
'Federated search' spaffed info all over Five Eyes chums
Three quarters of South Korea popped in online gaming raids
Records used to plunder game items, sold off to low lifes
Oz fed police in PDF redaction SNAFU
Give us your metadata, we'll publish your data
prev story

Whitepapers

Endpoint data privacy in the cloud is easier than you think
Innovations in encryption and storage resolve issues of data privacy and key requirements for companies to look for in a solution.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Advanced data protection for your virtualized environments
Find a natural fit for optimizing protection for the often resource-constrained data protection process found in virtual environments.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.