Economy servers are typically IRC serverswhere criminals and so-called "black hats" congregate to sell theirillegally obtained merchandise. They can be thought of much like abazaar of old, where the sellers announce their wares and their pricesin the hopes that buyers will choose them. These wares typicallyinclude stolen credit cards, identities, online gaming accounts, Website logins (such as Paypal and eBay), and other illegal goods. Becausethese servers are frequently tracked by law enforcement, the people whodo the trading have to be careful.
It has been observed that these servers rarely have a single fixedaddress. Commonly, the server migrates to a new address on a regularbasis, as frequently as every week. Presumably there is somepre-arranged pattern or a central source that tells loyal users wherethe current server is. It's not uncommon for a researcher to connect toan active economy server only to find it completely empty. This forceslaw enforcement and researchers to work much harder to track theactivity.
Sometimes, legitimate IRC servers are co-opted to serve as economyservers. An economy channel will be established on a small, legitimateserver set up for a game or event or something similar. It'sadvertised, people connect, trading is done, and, before long, thechannel is discovered by the server admin, who bans the users. Oncethat happens, they simply find another server and continue theiractivities.
Other times, servers are set up for the specific purpose of beingeconomy servers. Since hosting economy servers may potentially be alegal liability, I wouldn't be surprised if these were hosted on hackedservers or bot-infected computers. Again, these move quickly as they'refound and disinfected. Additionally, it's advantageous to the tradersto move on a regular basis to keep ahead of law enforcement.
This movement of economy servers shows something about thesecriminals: they are opportunistic. The ones who are frequently observedin turn move around frequently and sell to anybody who is willing tobuy. Typically, they will advertise the same wares in multiple channelson multiple servers to try and move what they have. This is partlybecause many of their products are time-sensitive – stolen credit cardsmay be cancelled and rendered useless after only a couple of days.