Hackers sold access to 170,000 compromised servers, many in the US

The new revelation comes from antivirus firm Kaspersky Lab, whose researchers reported last week that a black market website called xDedic was selling remote access to more than 70,000 compromised servers for as little as US$6.

Following the report, a user with the moniker AngryBirds shared several Pastebin lists of IP addresses along with dates that allegedly represented hacked servers sold on xDedic since Oct. 2014.

The combined lists contained around 176,000 unique IP addresses, 100,000 more than the Kaspersky Lab researchers gathered themselves from the black market website. Validating the lists was not easy, especially since xDedic only displays the first two octets of a server's IP address -- for example 111.111.*.*.

However, the researchers found enough correlations to suggest that the new database of hacked servers is real and was copied from xDedic around February by someone who had access to see the full IP addresses.

The discrepancy between the 70,000 IP addresses collected recently by the researchers and the 176,000 sent by the anonymous user could be explained by the fact that xDedic only publicly displayed servers that hadn't yet been sold when the researchers viewed the website.

A geographic analysis of the new list changes the picture of the most affected countries. Whereas Brazil and China occupied the first and second spots, respectively, for hacked server IP addresses during Kaspersky's initial analysis, when the new list is taken into account, those positions are occupied by the U.S., with over 60,000 hacked servers, and the U.K. with almost 9,000.

Servers from the U.S. and Western Europe are viewed by attackers as more valuable and would have likely sold faster. In fact, the top 10 most expensive servers still listed on xDedic were from the U.S. and ranged in price from $1,500 to $6,000.

It's hard to say why access to these servers is so expensive, but the researchers observed a high interest in servers associated with accounting, tax reporting and point-of-sale (PoS) software because they offer many opportunities for cybercriminals.

The new list, which displays full IP addresses, makes it easier for companies and network operators to check if any of their current or past machines were listed at some point on xDedic. Unfortunately, since it's now public, the list also makes it easier for other hackers to try and compromise the same vulnerable servers.