CLOP Ransomware

Original Issue Date:-July 23, 2020

Virus Type:-Ransomware

Severity:-High

It is reported that the ransomware named “CLOP” is active in attacking organizations/institutions across the globe. Post compromise this ransomware leaks information if negotiation deal of ransom fails. Recently the threat actors behind Clop have stolen and encrypted the sensitive information of various organizations and after failure of ransom payment, the stolen information was leaked on their 'CL0P^_- LEAKS' data leak site, hosted on dark web. The leaked information includes data backups, financial records, thousands of emails and vouchers etc.

After encryption CLOP ransomware appends “.Clop” extension in each file and generates a text file "ClopReadMe.txt" containing ransom note in each folder. CLOP ransomware uses RSA (Rivest-Shamir-Adleman) encryption algorithm and generated keys are stored on a remote server controlled by Clop operators.

Figure:1 Clop ransomware message

Updated versions of Clop have tried to expand their attack vectors through disabling and removing local security solutions such as Windows Defender and Microsoft Security Essentials etc. This ransomware has capability of installing additional password stealing Trojans and other malware infections.

Figure:2 Files encrypted by Clop

In most cases, Clop is distributed via fake software updates, trojans, cracks, unofficial software download sources, and spam emails. In the recent attack on an Indian conglomerate, it is suspected that the bug (CVE-2019-19781) in the Citrix Netscaler ADC VPN gateway was utilized to carry out the attack. Unfortunately, as of now no decryptor tool is available for Clop ransomware.

Indicators of compromise:

Hashes:

6d115ae4c32d01a073185df95d3441d51065340ead1eada0efda6975214d1920
6d8d5aac7ffda33caa1addcdc0d4e801de40cb437cf45cface5350710cde2a74
70f42cc9fca43dc1fdfa584b37ecbc81761fb996cb358b6f569d734fa8cce4e3
a5f82f3ad0800bfb9d00a90770c852fb34c82ecb80627be2d950e198d0ad6e8b
85b71784734705f6119cdb59b1122ce721895662a6d98bb01e82de7a4f37a188 (unpacked)
2ceeedd2f389c6118b4e0a02a535ebb142d81d35f38cab9a3099b915b5c274cb
00e815ade8f3ad89a7726da8edd168df13f96ccb6c3daaf995aa9428bfb9ecf1
0d19f60423cb2128555e831dc340152f9588c99f3e47d64f0bb4206a6213d579
408af0af7419f67d396f754f01d4757ea89355ad19f71942f8d44c0d5515eec8
7e91ff12d3f26982473c38a3ae99bfaf0b2966e85046ebed09709b6af797ef66
a867deb1578088d066941c40e598e4523ab5fd6c3327d3afb951073bee59fb02

Emails:

servicedigilogos@protonmail[d0t]com
managersmaers@tutanota[d0t]com
unlock@eqaltech[d0t]su
unlock@royalmail[d0t]su
unlock@goldenbay[d0t]su
unlock@graylegion[d0t]su
kensgilbomet@protonmail[d0t]com

Files Detection/aliases:

Ransom.Win32.CLOP.D
Ransom.Win32.CLOP.D
Ransom.Win32.CLOP.F
Ransom.Win32.CLOP.F.note
Ransom.Win32.CLOP.M
Ransom.Win32.CLOP.THBAAAI
Trojan.BAT.CLOP.A
Trojan.BAT.CLOP.A.component
Trojan.Win32.CLOP.A.note

For detailed IOC (Hashes, Files etc), please refer the links provide in references.

Countermeasures and Best practices for prevention:

Do not download and install applications from untrusted sources [offered via unknown websites/ links on unscrupulous messages]. Install applications downloaded from reputed application market only.
Update software and operating systems with the latest patches. Outdated applications and operating systems are the targets of most attacks.
Don't open attachments in unsolicited e-mails, even if they come from people in your contact list, and never click on a URL contained in an unsolicited e-mail, even if the link seems benign. In cases of genuine URLs close out the e-mail and go to the organization’s website directly through browser.
Install ad blockers to combat exploit kits such as Fallout that are distributed via malicious advertising.
Prohibit external FTP connections and blacklist downloads of known offensive security tools.
All operating systems and applications should be kept updated on a regular basis. Virtual patching can be considered for protecting legacy systems and networks. This measure hinders cybercriminals from gaining easy access to any system through vulnerabilities in outdated applications and software. Avoid applying updates / patches available in any unofficial channel.
Restrict execution of Power shell /WSCRIPT in an enterprise environment. Ensure installation and use of the latest version of PowerShell, with enhanced logging enabled. Script block logging and transcription enabled. Send the associated logs to a centralized log repository for monitoring and analysis.
https://www.fireeye.com/blog/threat-research/2016/02/greater_visibilityt.html
Establish a Sender Policy Framework (SPF) for your domain, which is an email validation system designed to prevent spam by detecting email spoofing by which most of the ransomware samples successfully reaches the corporate email boxes.
Application whitelisting/Strict implementation of Software Restriction Policies (SRP) to block binaries running from %APPDATA% and %TEMP% paths. Ransomware sample drops and executes generally from these locations.
Users are advised to disable their RDP if not in use, if required, it should be placed behind the firewall and users are to bind with proper policies while using the RDP.
Block the attachments of file types, exe|pif|tmp|url|vb|vbe|scr|reg|cer|pst|cmd|com|bat|dll|dat|hlp|hta|js|wsf
Consider encrypting the confidential data as the ransomware generally targets common file types.
Perform regular backups of all critical information to limit the impact of data or system loss and to help expedite the recovery process. Ideally, this data should be kept on a separate device, and backups should be stored offline.
Network segmentation and segregation into security zones - help protect sensitive information and critical services. Separate administrative network from business processes with physical controls and Virtual Local Area Networks.

References: