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Top 10 Malware August 2021

In August 2021, the MS-ISAC observed Blaknight’s return to the Top 10 Malware along with Hupigon, which made its first appearance in the Top 10. The Top 10 Malware variants comprise 73% of the total malware activity in August 2021, increasing 9% from July 2021. Shlayer and CoinMiner lead the Top 10 Malware. Shlayer and CoinMiner activity more than doubled from the previous month due to the resumption of activity in the education sector after summer vacation and are likely to continue their prevalence in the Top 10 Malware for the coming months.
top 10 malware august 2021 Malware notifications
top 10 malware august 2021 pie chart
In August 2021, malvertisement accounted for the greatest number of alerts. Malvertisement continues as the top initial infection vector due to Shlayer activity. Activity levels for malspam, malvertisement, and multiple increased, while activity for dropped decreased. Shlayer activity increased 177% from the previous month, while CoinMiner increased over 300% from the previous month. The increase in activity from these malware is due to the education sector resuming activities from summer vacation. Shlayer is a downloader and dropper for MacOS malware. It is primarily distributed through malicious websites, hijacked domains, and malvertizing posing as a fake Adobe Flash updater. CoinMiner is a cryptocurrency miner that uses Windows Management Instrumentation (WMI) and EternalBlue to spread across a network. CoinMiner uses WMI Standard Event Consumer scripting to execute scripts for persistence. CoinMiner spreads through malspam or is dropped by other malware.
top 10 malware august 2021 Initial infection vectors

Dropped – Malware delivered by other malware already on the system, an exploit kit, infected third-party software, or manually by a cyber threat actor. Gh0st and Mirai are examples of this vector.

Multiple – Malware that currently favors at least two vectors. Currently, CoinMiner, CryptoWall, Hupigon, and ZeuS are malware utilizing multiple vectors.

Malspam – Unsolicited emails, which either direct users to malicious web sites or trick users into downloading or opening malware. Top 10 Malware using this technique include Agent Tesla, Blaknight, and NanoCore.

Malvertisement – Malware introduced through malicious advertisements. Currently, Shlayer is the only Top 10 Malware using this technique.

Top 10 Malware and IOCs

Below are the Top 10 Malware ranked in order of prevalence. The respective indicators of compromise (IOCs) are provided to aid in detecting and preventing infections from these Top 10 Malware variants. Note: The associated URIs are aligned with malware’s respective domain(s) or IP(s) and increase the likelihood of maliciousness when found together. The URIs alone are not inherently malicious.

1. Shlayer

Shlayer is a downloader and dropper for MacOS malware. It is primarily distributed through malicious websites, hijacked domains, and malvertizing posing as a fake Adobe Flash updater.
All Shlayer domains follow the same pattern <api.random_name.com>. Below area several examples of domains Shlayer uses.

Domains

  • api[.]interfacecache[.]com
  • api[.]scalableunit[.]com
  • api[.]typicalconfig[.]com
  • api[.]standartanalog[.]com
  • api[.]fieldenumerator[.]com
  • api[.]practicalsprint[.]com
  • api[.]searchwebsvc[.]com
  • api[.]connectedtask[.]com
  • api[.]navigationbuffer[.]com
  • api[.]windowtask[.]com

2. CoinMiner

CoinMiner is a cryptocurrency miner that uses Windows Management Instrumentation (WMI) and EternalBlue to spread across a network. CoinMiner uses the WMI Standard Event Consumer scripting to execute scripts for persistence. CoinMiner spreads through malspam or is dropped by other malware.

3. Agent Tesla

Agent Tesla is a RAT that exfiltrates credentials, logs keystrokes, and captures screenshots from an infected computer.

4. NanoCore

NanoCore is a RAT spread via malspam as a malicious Excel XLS spreadsheet. As a RAT, NanoCore can accept commands to download and execute files, visit websites, and add registry keys for persistence.

5. Gh0st

Gh0st is a RAT used to control infected endpoints. Gh0st is dropped by other malware to create a backdoor into a device that allows an attacker to fully control the infected device.

6. Hupigon

Hupigon is a backdoor trojan that is usually dropped by other malware or is unknowingly downloaded via a malicious website. Some of this malware’s abilities include: allowing remote users to connect to the affected system and execute commands on the system, logging keystrokes, and stealing information, such as credentials.

7. Mirai

Mirai is a malware botnet known to compromise internet of things (IoT) devices in order to conduct large-scale DDoS attacks. Mirai is dropped after an exploit has allowed the attacker to gain access to a machine.

8. Zeus

ZeuS is a modular banking trojan which uses keystroke logging to compromise victim credentials when the user visits a banking website. Since the release of the ZeuS source code in 2011, many other malware variants have adopted parts of its codebase, which means that events classified as ZeuS may actually be other malware using parts of the ZeuS code.

9. CryptoWall

CryptoWall is a ransomware commonly distributed through malspam with malicious ZIP attachments, Java Vulnerabilities, and malicious advertisements. Upon successful infection, CryptoWall will scan the system for drive letters, network shares, and removable drives. CryptoWall runs on both 32-bit and 64-bit systems.

10. Blaknight

Blaknight, also known as HawkEye, is an Infostealer known for its keylogging capabilities for credential and banking theft.