August 28th, 2009
Source code for Skype eavesdropping trojan in the wild
Earlier this week, Swiss programmer Ruben Unteregger who has been reportedly working for a Swiss company ERA IT Solutions responsible for coding government sponsored spyware, has released the source code of a trojan horse that injects code into the Skype process in order to convert the incoming and outgoing voice data into an encrypted MP3 available at the disposal of the attacker.
Here’s how the trojan, currently detected as Trojan.Peskyspy, works:
“When the Trojan is executed, it injects a thread into the Skype process and hooks a number of API calls, allowing it to intercept all PCM audio data going between the Skype process and underlying audio devices. Note: Since the Trojan listens to the data coming to and from the audio devices, it gathers the audio independently of any application-specific protocols or encryption applied by Skype when it passes voice data at the network level.
Note: The incoming and outgoing audio data are stored in separate .mp3 files. The Trojan also opens a back door on the compromised computer, allowing an attacker to perform the following actions:
- Send the .mp3 to a predetermined location
- Download an updated version
- Delete the Trojan from the compromised computer”
Skype is often dubbed a “national security threat” by governments all across the globe due to their — at least publicly acknowledged — inability to crack the 256-bit encryption VoIP calls.
And while some of these governments are reportedly spending surreal amounts of tax payer’s money (Rental of the Skype-Capture-Unit per month and instance EUR 3.500) in order to achieve their objectives, others are taking the cost-effectiveness path by attacking the weakest link in the process - the end user infected with a targeted DIY government sponsored spyware recording all ongoing and incoming Skype calls, thereby bypassing the need to attack the encryption algorithm.
Dancho Danchev is an independent security consultant and cyber threats analyst, with extensive experience in open source intelligence gathering, malware and cybercrime incident response. He's been an active security blogger since 2007, and maintains a popular security blog. See his full profile and disclosure of his industry affiliations.
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