Feeds

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

Covert messages exploit TCP

Boost IT visibility and business value

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. ®

Gartner critical capabilities for enterprise endpoint backup

More from The Register

next story
Microsoft: We plan to CLEAN UP this here Windows Store town
Paid-for apps that provide free downloads? Really
Snowden on NSA's MonsterMind TERROR: It may trigger cyberwar
Plus: Syria's internet going down? That was a US cock-up
Who needs hackers? 'Password1' opens a third of all biz doors
GPU-powered pen test yields more bad news about defences and passwords
e-Borders fiasco: Brits stung for £224m after US IT giant sues UK govt
Defeat to Raytheon branded 'catastrophic result'
Hear ye, young cyber warriors of the realm: GCHQ wants you
Get involved, get a job and then never discuss work ever again
Chinese hackers spied on investigators of Flight MH370 - report
Classified data on flight's disappearance pinched
Microsoft cries UNINSTALL in the wake of Blue Screens of Death™
Cache crash causes contained choloric calamity
prev story

Whitepapers

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.
7 Elements of Radically Simple OS Migration
Avoid the typical headaches of OS migration during your next project by learning about 7 elements of radically simple OS migration.
BYOD's dark side: Data protection
An endpoint data protection solution that adds value to the user and the organization so it can protect itself from data loss as well as leverage corporate data.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?