The man responsible for a recent cybercrime bust shared his experiences on Wednesday at the RSA conference in San Francisco.

FBI agent Keith Mularski told a panel at the conference about his two-year undercover experience as a member and later moderator of the cybercrime forum 'Dark Market'.

The forum was shut down last October following the arrest of nearly all its founders and administrators. Officials estimate that the bust led to 60 arrests and more than $70m in fraud averted.

Much of that was due to the work of Mularski, who penetrated the highest ranks of the forum's administration under the codename 'Master Splyntr'. Using the persona of an unknown hacker, Mularski eventually rose to obtain moderator status on the forum and host the actual site on FBI servers before finally shutting it down.

During that time, Mularski witnessed the site become what he described as a "one-stop shop" for crimes ranging from credit card theft to ID and passport forgery. The site traded in not only bank and credit card details, but also hardware and software for creating fake payment cards and phony documents.

"This was basically a supermarket for cybercrime where you could get anything you wanted for fraud," he explained.

Mularski then went on to describe the complex structure of the operation, which functioned much like an organised gang.

Dark Market's structure was headed by a small group of founding administrators. Reporting to the administrators were several moderators who oversaw operations on the site. Below the moderators were the reviewers in charge of testing for the authenticity of the data being traded.

The users were then divided into two categories: the reviewed vendors who sold the illegal materials and the users who purchased them.

Aside from the money itself being exchanged, reputation was the main currency in Dark Market. Users who defrauded others or sold non-working products could be banned from the site, while those who routinely offered quality data would see their status in the community improve.

Often, said Mularski, vendors would offer payment or free materials to reviewers in order to improve their standings.

Mularski's Master Splyntr persona was able to raise his standing in Dark Market by offering support services. Claiming to have a background in spamming and hosting, Master Splyntr gained favour with administrators when, following attacks from rival forums, Mularski offered to host Dark Market on his own servers, a move which proved critical in the shutdown of the gang's operation.