Hunt for hidden web messages goes on

Tuesday July 16, 2002 10:30

by Pat C

More 'justification' for snooping?

Yet more reasons why we should roll over & let our betters spy on all our emails. Gee & I thought al-Qaeda communicated by carrier pigeon. Pat

Hunt for hidden web messages goes on

18:13 12 July 02

NewScientist.com news service

Computer enthusiasts have been searching for messages hidden in web site images following new claims that the al-Qaeda terrorist network is using this technique - steganography - to communicate.

However, one expert in the field warns the images that have been flagged up as suspicious after initial examination are almost certain to be cleared after full analysis. Peter Honeyman, at the University of Michigan, told New Scientist: "You get a lot of these. We call them false positives."

On 10 July, USA Today reported that US intelligence officers believe images hosted on a pro-Islamic and anti-American web site called Azzam contain secret messages. There are many free programs available that can be used to lock password-protected information into image files.

The claim prompted computer enthusiasts to scrutinise the images for signs that they have been altered, again using free programs available online. One US computer student has posted preliminary results of his search to the mailing list Politechbot, suggesting that there are many tampered images on the Azzam site.

Cracking passwords

But Honeyman says to confirm the existence of hidden messages it is necessary to crack the password used to insert the message. This is done by searching through all possible passwords until you find the right one and requires a large amount of computing power.

Niels Provos, who is one of Honeyman's students and has developed a number of steganographic tools says: "Web images are generally of poor-quality leading to a higher false positive rate." He adds that their small size limits their information capacity, making them unattractive for steganography.

The same USA Today report says that US officials also believe al-Qaeda operatives have uploaded 2300 images containing encrypted information to the internet auction site eBay since the start of 2002.

Honeyman and Provos are particularly sceptical about this claim because they conducted an extensive search of eBay in November 2001 and found absolutely no evidence of steganography.

Will Knight

This story is from NewScientist.com's news service - for more exclusive news and expert analysis every week subscribe to New Scientist print edition.

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Hunt for hidden web messages goes on