A new strain of ransomware, OphionLocker, generates a unique hardware identifier for each new infected machine so that it can avoid hitting the same victim twice, according to new research from KnowBe4, a Florida-based security awareness training firm.
"This we have not seen before," said KnowBe4 CEO Stu Sjouwerman, who suggested that the crooks have a brand reputation to maintain.
If the ransomware attacked the same machine twice, re-encrypting already encrypted files, they might not be able to recover the data.
"The ransomware people are very focused on their customer service," he said. "It's in their best interest that word get out that if you pay, you will get your files back."
"The irony is thick," he added.
OphionLocker uses infected websites to install itself on unpatched computers, then encrypts the victim's data with strong opensource Cropto ++ elliptical curve cryptography. The cost to recover the files is typically around 1 Bitcoin, or about US $333.
According to KnowBe4, the ransom amount varies based on the victim's country, with the U.S. having the highest rates.
After victims are infected and their files encrypted, the malware sends the victims to the ransomware site where they are given payment instructions.
However, the ransomware does not secure delete the files or remove shadow volume copies, so a file recovery tool or a program like Shadow Explorer could be used to recover the files.
Meanwhile, another new piece of ransomware, TorrentLocker, is gathering steam, said Sjouwerman.
"A new group is honing their software, optimizing their systems, and once everything is in gear, they will attack the U.S.," he said.
TorrentLocker was first spotted in the UK and Australia earlier this year and has since spread to Italy, the Czech Republic, Germany, and Turkey, he said.
According to a white paper published today by ESET, a security research firm based in Bratislava in the Slovak Republic, the criminals made between US$292,700 and US$585,401 in Bitcoins from this particular infection. Around 1.45 percent of victims paid a ransom, or 570 out of 39,670 infections.
The ransom amounts for TorrentLocker varied, up to more than 4 Bitcoins, or around US $1,500. The infection vector was a Zip file that was either attached to an email message, or downloaded from the Web.
The email messages tried to fool recipients into thinking the attachments were unpaid invoices, tracking information for package deliveries or unpaid speeding tickets -- or asked the victims to click on links purporting to be local business or government websites.
The criminals were careful to target only people from particular countries, ESET researcher Marc-Etienne Léveillé said in the white paper, with the spam emails localized to the victim's geographical area, and the malicious websites filtering visitors based on their IP addresses.
An early version of TorrentLocker had a flaw that was discovered in September, and security researchers released a tool to extract the keystream and automate the decryption process. TorrentLocker's authors reacted by changing the encryption method.
"The bad guys don't go away," said KnowBe4's Sjouwerman. "They get mad and then they come back with something better."