Terrorist groups, including Saudi dissident Osama bin Laden, are using coded messages in pornography and sports websites to help agents to plot guerrilla attacks, say American security experts.
Encrypted messages on internet bulletin boards have replaced the traditional cloak-and-dagger methods of dead-letter drops.
Bin Laden, a dissident Saudi businessman, has been
indicted for the 1998 bombing of two United States embassies in East Africa and named as a suspect in last year's bombing of an American warship in Yemen.
Cyber-intelligence expert Ben Venzke, of American security company iDefense, said internet bulletin boards carrying pornographic and sports information were most popular because of the huge number of hits they received.
The technique involves using encryption, which scrambles data and hides it in existing images. The party accessing the data unlocks it with an agreed computerised "key."
New Zealand security expert Arjen De Landgraaf, of E-secure-it, said it was feasible for terrorist groups to communicate in this way and almost impossible to detect.
"Terrorists know that their phones are being tapped, so for them it's a perfect way to get the information through."
He said Governments around the world were struggling to control the internet, particularly the right to monitor e-mail, in an effort to thwart dissident attacks.
But he said even if Governments were able to get access to the keys to encryption, a message could still get through by being double-encrypted.
"You can still encode anything within an encryption."
CIA information operations manager John Serabian told a US Government panel last year that groups such as Hizbollah, Hamas, and bin Laden's were using computerised files, email and encryption to communicate.
"Terrorists already use the internet to communicate, to raise funds, recruit, and gather intelligence."
Last August the Weekend Herald revealed what police believed was a clandestine cell of possible terrorists in Mt Albert.
Some of the 20 people the police identified were thought to have links to sympathisers of bin Laden.
It was suspected the group was plotting to hit the Sydney Olympics.
