Ever since criminal-favourite Liberty Reserve was shut down last May, fraudsters have been scrambling around for an alternative, says RSA in a blog post.

The most obvious candidate, bitcoin, is being avoided by many because of a lack of anonymity and worries, in the wake of the Silk Road takedown, about seizures. Meanwhile, another potential option, Perfect Money, is of "questionable background".

So, crooks are using forum-specific currencies, allowing them to safely transact within their own community, under the supervision of an administrator, RSA's Fraud Intelligence agents have found.

One underground board developed the 'Musd' currency in November. Forum members can use the currency to purchase items and services from each other. The currency provides a built-in escrow-service and guarantees anonymity. The administrator vouches for the currency system and is responsible for all its operations.

Users exchange funds to or from Musd through exchange agents. Two verified exchange agent services currently work with Musd, with one offering to cash out the currency for hard cash in person at an office in Kiev, Ukraine, says RSA.

Another option, the United Payment System currency appears to be shared by four different Russian language forums, with each designating its own sub-currency. Each forum has its own official exchange agent, and each of these has an administrator. Funds can be added or cashed out via the agents with cash out options including pre-paid cards.

Says RSA's Daniel Cohen: "The advent of new private financial systems and currencies in the Russian-language cybercrime community is a trend indicating a stronger level of collaboration, cooperation and sophistication amongst individual fraudsters and between fraudster boards in the cybercrime world.

"These new internal currencies are carefully administered and secured, ensuring a high level of anonymity in transaction and hiding the user identities, making it more difficult for law enforcement to trace, block, or seize funds and accounts."