The world of cybercrime is thriving on spam and the means of distributing it, say security experts.

A panel of security and anti-spam experts discussed the market that has grown around spam, malware and identity theft today at the RSA security conference in San Francisco.

The most serious of those problems is the legions of remotely-controlled botnet PCs, according to Joe St Sauver of the Internet 2 project.

"When you think about the problem that spammers face, as soon as they send mail in any sort of volume, [anti-spam groups] black-list them, so their IP space becomes unusable for their core mission," he said.

"So they're going to need some other channel for sending out that spam, and that usually means hijacked consumer PCs."

With the rise in value of botnets, the market for the malware that controls those botnets has also thrived. Bot-hungry spammers are now hiring botnet operators and malware distributors as affiliates, paying for each infection.

"The days of the individual 'Lone Ranger' spammer who does it all are pretty much gone," said St Sauver.

"So what you have now is a spammer affiliate program with franchises."

The market for this is further compounded by the climate in developing countries where there are millions of poorly-maintained PCs and a new crop of educated people turning to crime rather than a less lucrative professional career.

And it is not only criminal groups that are drawn into the world of cybercrime. The need to launder the windfall of cash from malware and identity theft operations has lead to an explosion in the recruiting of 'money mules', people who take the stolen funds into their own account and then send the money as a wire transfer to the criminal groups.

"The fundamental problem that they have is that the accounts these cards are sitting in are in specific geographies," explained Lawrence Baldwin, chief forensics officer for mynetwatchman.com.

"It is far more effective for them to have someone on the ground, because that will help them get past the anti-fraud detections at the bank."

Because the mule is essentially laundering money, the criminals are protected from law enforcement, while the mules are often arrested and prosecuted without ever knowingly committing a crime.

"Many of them are victims in the same way that people who have had their computers compromised are victims," said St Sauver.

"There are citizens out there who need someone to come out and not arrest them for being complicit, but to help them clean out their systems."