Feeds

Hiding secret messages in internet traffic: a new how-to

Covert messages exploit TCP

Beginner's guide to SSL certificates

Researchers have demonstrated a new way to hide secret messages in internet traffic that can elude even vigilant network operators.

The process is a network application of steganography, which is the ancient science and art of hiding messages in documents, pictures and other media in a way that can be easily detected by the intended recipient, but not by third parties. The researchers from the Warsaw University of Technology have found a way to apply the principle to network traffic by exploiting design weaknesses in TCP, or transmission control protocol.

RSTEG, short for Retransmission Steganography, works by manipulating the back-and-forth sequence and messages exchanged each time an internet packet is sent. Typically, a computer on the receiving end sends a confirmation each time one is successfully transmitted. RSTEG works by deliberately withholding the acknowledgment, which then prompts the packet to be resent.

"In the context of RSTEG, a sender replaces original payload with a steganogram instead of sending the same packet again," the paper, authored by Wojciech Mazurczyk, Miłosz Smolarczyk, and Krzysztof Szczypiorski, states. "When the retransmitted packet reaches the receiver, he/she can then extract hidden information."

The technique has important implications for network security because it can be used by attackers to conceal the leakage of confidential information, the paper warns. It goes on to detail four scenarios in which the attack can be used, including one that requires no control of intermediate nodes. The other three are harder to pull off, but they are also harder to detect by third parties.

"No real-world steganographic method is perfect; whatever the method, the hidden information can be potentially discovered," the researchers write. "In general, the more hidden information is inserted into the data stream, the greater the chance that it will be detected, for example, by scanning the data flow or by some other seganalysis methods."

To evade detection, those using the technique must limit the number of retransmissions to non-suspicious levels.

Steganography dates back to the Fifth Century BC at least, when Greek messengers buried messages on wax tablets before sealing them with beeswax. In more recent times, it's been used to sneak data into all kinds of electronic media, including digital photographs and executable files. The same Polish researchers who described RSTEG also developed a similar technique targeting voice over IP traffic.

While RSTEG works only with TCP, the principle can be applied to other protocols as well, including those for wireless networks. A PDF of the paper is available here. ®

Protecting users from Firesheep and other Sidejacking attacks with SSL

More from The Register

next story
Spies would need SUPER POWERS to tap undersea cables
Why mess with armoured 10kV cables when land-based, and legal, snoop tools are easier?
Early result from Scots indyref vote? NAW, Jimmy - it's a SCAM
Anyone claiming to know before tomorrow is telling porkies
TOR users become FBI's No.1 hacking target after legal power grab
Be afeared, me hearties, these scoundrels be spying our signals
Jihadi terrorists DIDN'T encrypt their comms 'cos of Snowden leaks
Intel bods' analysis concludes 'no significant change' after whistle was blown
Home Depot: 56 million bank cards pwned by malware in our tills
That's about 50 per cent bigger than the Target tills mega-hack
Hackers pop Brazil newspaper to root home routers
Step One: try default passwords. Step Two: Repeat Step One until success
China hacked US Army transport orgs TWENTY TIMES in ONE YEAR
FBI et al knew of nine hacks - but didn't tell TRANSCOM
Microsoft to patch ASP.NET mess even if you don't
We know what's good for you, because we made the mess says Redmond
NORKS ban Wi-Fi and satellite internet at embassies
Crackdown on tardy diplomatic sysadmins providing accidental unfiltered internet access
prev story

Whitepapers

Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
WIN a very cool portable ZX Spectrum
Win a one-off portable Spectrum built by legendary hardware hacker Ben Heck
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
Protecting users from Firesheep and other Sidejacking attacks with SSL
Discussing the vulnerabilities inherent in Wi-Fi networks, and how using TLS/SSL for your entire site will assure security.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.