A group calling itself XMR Squad has spent all last week launching DDoS attacks against German businesses and then contacting the same companies to inform them they had to pay €250 ($275) for "testing their DDoS protection systems."

German DDoS protection firm Link11 reported attacks against DHL, Hermes, AldiTalk, Freenet, Snipes.com, the State Bureau of Investigation Lower Saxony, and the website of the state of North Rhine-Westphalia.

DDoS attacks were powerful and well aimed

The attack against DHL Germany was particularly effective as it shut down the company's business customer portal and all APIs, prompting eBay Germany to issue an alert regarding possible issues with packages sent via DHL.

"They seem to know what to hit," said Daniel Smith, security researcher for Radware, and one of the persons currently keeping tabs of the attacks.

The group sent emails to all the companies it targeted. In the emails, they didn't ask for a ransom to stop the attacks, but a fee for having already carried out what they called a DDoS protection test.

Usually, these types of groups launch DDoS attacks and then send emails to their victims requesting for payments to stop the attacks. XMR Squad's emails looked like invoices for unrequested DDoS tests.

Furthermore, the ransom note didn't include payment instructions, which is weird, to say the least. DDoS ransoms are usually handled in Bitcoin or another anonymous cryptocurrency. It was strange to see the group ask for payment in Euros, as the group's name included the term XMR, the shortname for Monero, an anonymous cryptocurrency.

Group disappears after one week

While the group advertised on Twitter that their location was in Russia, a German reporter who spoke with the group via telephone said "the caller had a slight accent, but spoke perfect German."

To the same reporter, the group also claimed they carried out the attacks only to get public attention. The attention they got wasn't the one they expected, as their hosting provider took down their website, located at xmr-squad.biz.

Following ridicule from fellow hackers, who made fun of the group for failing to understand how a DDoS extortion works, the group closed their Twitter account earlier today.

German companies often targeted by DDoS extortionists

Germany, in particular, has been the target of several DDoS blackmailers in the past year. In January and February, a group calling itself Stealth Ravens launched DDoS-for-Bitcoin ransom attacks.

Link11, who tracked those attacks, claimed the group used a DDoS botnet built with the Mirai IoT malware and asked for 5 Bitcoin ($6,000) to stop attacks.

Last year in June, another group named Kadyrovtsy also targeted German businesses, launching attacks of up to 50 Gbps. This group began DDoS ransom attacks a month earlier by first targeting Polish banks.

New groups emerging after DD4BC and Armada Collective's demise

All these groups are following the same modus operandi perfected by groups like DD4BC and Armada Collective. These two groups appeared in the summer and autumn of 2015 and targeted companies worldwide. In January 2016, Europol arrested suspects believed to be DD4BC members in Bosnia and Herzegovina. Following the arrests, both groups became inactive.

After the demise of these two main groups, there was a wave of copycats [1, 2, 3, 4, 5] that used their respective reputation to extort payments from companies, in many cases without even possessing any DDoS capabilities.

Stealth Raven and Kadyrovtsy are part of the new wave of DDoS-for-Bitcoin extortionists that managed to build their own name, albeit they haven't reached the same level of notoriety as DD4BC or Armada Collective.

Update [May 4, 2017]: New XMR Squad DDoS ransom attacks have been spotted in the wild. This time around, the group is asking for ransoms going from 3 to 20 Bitcons [1, 2].