Pierluigi Paganini August 01, 2018

The security experts from Sophos have published a report on the multimillion-dollar black market business for crooks, they analyzed the SamSam ransomware case as a case study.

The researchers that have tracked Bitcoin addresses managed by the crime gang discovered that crooks behind the SamSam ransomware had extorted nearly $6 million from the victims since December 2015 when it appeared in the threat landscape.

“SamSam has earned its creator(s) more than US$5.9 Million since late 2015.
74% of the known victims are based in the United States. Other regions known to have
suffered attacks include Canada, the UK, and the Middle East.” reads the report published by Sophos.

“The largest ransom paid by an individual victim, so far, is valued at US$64,000, a
significantly large amount compared to most ransomware families.”

Sophos tracked the Bitcoin addresses reported in all the SamSam versions it has spotted and discovered that 233 victims paid an overall amount of $5.9 million, the security firm also estimated that the group is netting around $300,000 per month.

“In total, we have now identified 157 unique addresses which have received ransom payments as well as 89 addresses which have been used on ransom notes and sample files but, to date, have not received payments,” continues the report published by Sophos.

“By analyzing the payments, and comparing this with ransom notes at the time, we can estimate the number of individual victims who have chosen to pay at least some of the ransom amount stands at 233 as of July 19th 2018. With an estimated 1 new victim being attacked each day, we believe that roughly 1 in 4 victims pay at least some of the ransom. “

SamSam ransomware payments

The attackers deploy the SamSam ransomware manually by compromising RDP on the target machine, this aspect makes SamSam infections different from the ones associated with other ransomware that leverages spam campaigns or malvertising.

The attackers carry on brute-force attacks on RDP of the target system, some time they leverage credentials obtained from other data breaches typically offered for sale on the dark web.

Once compromised a system inside the targeted organization, the SamSam search for other machines to infect while stealing credentials.

When operators discover a potential target they manually deploy SamSam using tools like PSEXEC and batch scripts.

The following diagram shows the different steps of the latest SamSam variant for which the initial infection vector is still unclear.

Once infected the largest number of systems in the targeted organization, operators attempt to offer a complete clean up of the infected systems for a special price.

The highest estimate has been US$850,000 worth of bitcoin for the decryption keys.

The encryption process first involves most valuable data thanks to a multi-tiered priority system, SamSam ransomware doesn’t encrypt Windows system-related files.

Since its discovery, the SamSam ransomware targeted large organizations, including hospitals and educational institutions.

Sophos provides the following recommendations to secure the network of organizations against the SamSam ransomware:

• regularly patch against known vulnerabilities for the applications and operating systems;
• keep regular backups;
• use multi-factor authentication;
• restrict access to RDP(on port 3389);

Pierluigi Paganini

(Security Affairs – ransomware, malware)

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