Top 10 Malware March 2021

In March 2021, the MS-ISAC observed Blaknight and Danabot’s return to the Top 10, while CopperStealer made its first appearance. The Top 10 Malware variants comprise 77% of the total malware activity in March 2021, increasing 1% from February 2021. Shlayer is highly likely to continue its prevalence in the Top 10 Malware due to the continued increase of schools and universities returning to in-person teaching or a hybrid model.



In March 2021, malvertisement accounted for the greatest number of alerts. Malvertisement continues as the top initial infection vector due to Shlayer activity. Shlayer returned to the Top 10 Malware after new evidence resulted in it being reclassified as a trojan downloader compared to an adware dropper. Activity levels for malspam, malvertisement, and multiple increased, while activity for dropped decreased. It is highly likely that malvertisement will remain the primary infection vector as the Shlayer campaign pans out.



Dropped – Malware delivered by other malware already on the system, an exploit kit, infected third-party software, or manually by a cyber threat actor. Jupyter is the only malware dropped.

Multiple – Malware that currently favors at least two vectors. Currently, CoinMiner and ZeuS are the malware utilizing multiple vectors. ZeuS is dropped by other malware, but it is also delivered via malvertisement.

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

Malvertisement – Malware introduced through malicious advertisements. Currently, Shlayer and CopperStealer are 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 . Below are several examples of domains Shlayer uses.


  • 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. 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.


  • 176.121.14[.]151


  • /gate.php

4. Agent Tesla

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

5. Jupyter

Jupyter is an infostealer downloaded by masquerading as legitimate software. It primarily targets browser data in browsers such as Chrome, Chromium, and Firefox and has full backdoor functionality.

6. Snugy

Snugy is a PowerShell-based backdoor allowing the attacker to obtain the system’s hostname and run commands. This backdoor communicates through a DNS tunneling channel on the compromised server.

7. Danabot

Danabot is a banking trojan spread via malspam using malicious macros in Microsoft Office. It has the ability to steal credentials, collect information on the infected system, use web injection, and drop other malware, such as GootKit.

8. Hancitor

Hancitor, also known as Chanitor or Tordal, is a downloader that spreads through malspam containing malicious Microsoft Office documents, links, and attachments. This malware has been known to download additional malware, such as Pony, Ursnif, and Vawtrak.


  • Plogesuct[.]com
  • Cationfrob[.]ru
  • Scientemplud[.]ru
  • Orialoussin[.]ru
  • Conaboory[.]ru
  • Iderfeirel[.]com
  • Lpertion[.]com


  • /4/forum.php
  • /8/forum.php

9. CopperStealer

CopperStealer is an infostealer that infects victims via malvertisement. It has multiple capabilities including anti-analysis, account credential theft (specifically service providers like Facebook, Instagram, Twitter, Google, Amazon, and PayPal), data exfiltration, and the ability to drop other malware, such as Smokeloader.

10. Blaknight

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