Curumim Ransomware

Posted: November 9, 2017

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Ranking:	17,507
Threat Level:	2/10
Infected PCs:	700

First Seen:	February 7, 2019
Last Seen:	October 12, 2023
OS(es) Affected:	Windows

The Curumim Ransomware is a new version of the Hidden Tear Trojan, which can block files on your computer and create different forms of ransom notes, such as pop-ups, desktop backgrounds or text messages. Like other versions of the Hidden Tear family, the Curumim Ransomware has a significantly lesser impact against victims who keep secure backups of their data, which allows them to restore content without decrypting it. A majority of anti-malware programs also can identify and remove the Curumim Ransomware at any stage of an infection.

Skin-Deep Ethnic Diversity in Trojans

The periodic targeting of Brazilian PC owners with data-locking attacks has a new data point for November, with its threat actor showing slightly more familiarity with the region than most cybercrooks. Although a fresh and edited version of Hidden Tear is far from new to malware experts, the Curumim Ransomware is a slightly rarer example of a variant that has a custom theme that's highly specific to the region it's attacking. Besides these cosmetic additions, the Curumim Ransomware remains a representative of the Hidden Tear archetype by using AES data-enciphering to encode and block files, possibly permanently.

The Curumim Ransomware's executable isn't disguising itself (unlike the fake 'sound driver' example seen in another Hidden Tear Trojan, the Foxy Ransomware), and most likely, is being distributed with the assistance of another threat that installs it automatically. When the installation finishes, the Curumim Ransomware loads a payload that includes encrypting files on the infected PC, excluding essential formats and locations, but including media like documents and pictures. The Curumim Ransomware also creates new extensions ('.curumim') for the names of the newly non-opening files.

The final addition to the Curumim Ransomware's payload is a non-standard ransom note that malware experts haven't seen in other campaigns, even in other ones targeting the same nation of Brazil. This message includes a customized image depicting a cartoon child (which references the 'curumim,' meaning 'child' or 'infant' in the language of the Tupi people) and a message asking you to contact the threat actor's e-mail within one day. The Trojan also claims that your files will not be recoverable beyond this deadline, even though malware experts can't confirm the presence of any automated, data-deleting feature (which is not a default function of the Hidden Tear project).

Keeping Your Files Safe from the Pranks of Children

Cultural references and relatively competent usage of the Brazilian Portuguese are traits that make the Curumim Ransomware, more than likely, the project of a threat actor who's native or otherwise highly familiar with Brazil. Although malware analysts can't corroborate any attacks delivering the Curumim Ransomware to the public at large, file-locking Trojans often depend on one of a handful of infection vectors. These include:

E-mail attachments may pretend to be articles or documentation while concealing bad macros or other content that's suitable for installing threats like the Curumim Ransomware. Most anti-malware security products can detect these exploits and fake files.
Compromised websites sometimes utilize exploit kits to exploit vulnerabilities through your browser appropriate for drive-by-downloads. Disabling scripts and installing patches as recommended are two ways of protecting your PC from such attacks.

Anti-malware software also may remove the Curumim Ransomware from an infected computer safely, although additional work may be necessary for unlocking your media. Malware experts report good rates of success with free decryption utilities versus most versions of Hidden Tear.

Since it's just starting to be identifiable as a functional threat to PC users, the Curumim Ransomware has many aspects left to explore, including what types of victims its author is targeting for extortion. However, whether your computer activities are for work or pleasure, there's much to be said for the power of a consistent backup schedule.

Technical Details

Additional Information

The following URL's were detected:

wwmnnl.com