Data Encrypted for Impact

Adversaries may encrypt data on target systems or on large numbers of systems in a network to interrupt availability to system and network resources. They can attempt to render stored data inaccessible by encrypting files or data on local and remote drives and withholding access to a decryption key. This may be done in order to extract monetary compensation from a victim in exchange for decryption or a decryption key (ransomware) or to render data permanently inaccessible in cases where the key is not saved or transmitted.(Citation: US-CERT Ransomware 2016)(Citation: FireEye WannaCry 2017)(Citation: US-CERT NotPetya 2017)(Citation: US-CERT SamSam 2018)

In the case of ransomware, it is typical that common user files like Office documents, PDFs, images, videos, audio, text, and source code files will be encrypted (and often renamed and/or tagged with specific file markers). Adversaries may need to first employ other behaviors, such as [File and Directory Permissions Modification](https://attack.mitre.org/techniques/T1222) or [System Shutdown/Reboot](https://attack.mitre.org/techniques/T1529), in order to unlock and/or gain access to manipulate these files.(Citation: CarbonBlack Conti July 2020) In some cases, adversaries may encrypt critical system files, disk partitions, and the MBR.(Citation: US-CERT NotPetya 2017) 

To maximize impact on the target organization, malware designed for encrypting data may have worm-like features to propagate across a network by leveraging other attack techniques like [Valid Accounts](https://attack.mitre.org/techniques/T1078), [OS Credential Dumping](https://attack.mitre.org/techniques/T1003), and [SMB/Windows Admin Shares](https://attack.mitre.org/techniques/T1021/002).(Citation: FireEye WannaCry 2017)(Citation: US-CERT NotPetya 2017) Encryption malware may also leverage [Internal Defacement](https://attack.mitre.org/techniques/T1491/001), such as changing victim wallpapers, or otherwise intimidate victims by sending ransom notes or other messages to connected printers (known as "print bombing").(Citation: NHS Digital Egregor Nov 2020)

In cloud environments, storage objects within compromised accounts may also be encrypted.(Citation: Rhino S3 Ransomware Part 1)

Platforms: Linux
macOS
Windows
IaaS
Tactics:
phase_name: impact

Detection:
Use process monitoring to monitor the execution and command line parameters of binaries involved in data destruction activity, such as vssadmin, wbadmin, and bcdedit. Monitor for the creation of suspicious files as well as unusual file modification activity. In particular, look for large quantities of file modifications in user directories.

In some cases, monitoring for unusual kernel driver installation activity can aid in detection.

In cloud environments, monitor for events that indicate storage objects have been anomalously replaced by copies.

References:
source_name: mitre-attack
description: Baskin, B. (2020, July 8). TAU Threat Discovery: Conti Ransomware. Retrieved February 17, 2021.
source_name: CarbonBlack Conti July 2020
description: Berry, A., Homan, J., and Eitzman, R. (2017, May 23). WannaCry Malware Profile. Retrieved March 15, 2019.
source_name: FireEye WannaCry 2017
description: Gietzen, S. (n.d.). S3 Ransomware Part 1: Attack Vector. Retrieved April 14, 2021.
source_name: Rhino S3 Ransomware Part 1
description: NHS Digital. (2020, November 26). Egregor Ransomware The RaaS successor to Maze. Retrieved December 29, 2020.
source_name: NHS Digital Egregor Nov 2020
description: US-CERT. (2016, March 31). Alert (TA16-091A): Ransomware and Recent Variants. Retrieved March 15, 2019.
source_name: US-CERT Ransomware 2016
description: US-CERT. (2017, July 1). Alert (TA17-181A): Petya Ransomware. Retrieved March 15, 2019.
source_name: US-CERT NotPetya 2017
description: US-CERT. (2018, December 3). Alert (AA18-337A): SamSam Ransomware. Retrieved March 15, 2019.
source_name: US-CERT SamSam 2018