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Executive Summary

MyDoom is an infamous computer worm first noted in early 2004. This malware has been featured in top ten lists of the most destructive computer viruses, causing an estimated $38 billion in damage. Although now well past its heyday, MyDoom continues to be a presence in the cyber threat landscape.

While not as prominent as other malware families, MyDoom has remained relatively consistent during the past few years, averaging approximately 1.1 percent of all emails we see with malware attachments. We continue to record tens of thousands of MyDoom samples every month. The vast majority of MyDoom emails come from IP addresses registered in China, with the United States running a distant second. These emails are sent to recipients across the world, mostly targeting high tech, wholesale, retail, healthcare, education, and manufacturing industries.

This blog tracks MyDoom activity in recent years and focuses on trends during the first six months of 2019.

2015 through 2018

MyDoom’s method of propagation is through email using SMTP. We compared emails containing MyDoom attachments with emails containing any type of malware attachment. In the four-year period from 2015 through 2018, an average of 1.1 percent of malicious emails contained MyDoom. When reviewing individual malware samples during the same period, MyDoom held an average of 21.4 percent for all individual malware attachments seen through malicious emails.

Why is the percentage of MyDoom emails so much lower than the percentage of MyDoom attachments? Because many malicious email campaigns carry the same malware sample across messages to hundreds or thousands of recipients. MyDoom is polymorphic and tends to have different file hashes for each of the emails we find. Therefore, while the number of MyDoom emails is relatively low, the number of samples is comparatively higher when compared to other malware distributed through email. Table 1 contains the statistics for 2015 through 2018.

Year MyDoom emails Total emails with malware % of MyDoom emails MyDoom samples Total malware samples % of MyDoom samples 2015 574,674 27,599,631 2.1% 87,119 615,386 14.2% 2016 589,107 77,575,376 0.8% 142,659 960,517 14.9% 2017 309,978 79,599,864 0.4% 95,115 340,433 27.9% 2018 663,212 64,919,295 1.0% 150,075 528,306 28.4%

Table 1. MyDoom statistics from 2015 through 2018.

Image 1. MyDoom activity levels in 2015.

Image 2. MyDoom activity levels in 2016.

Image 3. MyDoom activity levels in 2017.

Image 4. MyDoom activity levels in 2018.

MyDoom Activity in 2019

The first six months of 2019 for MyDoom activity reveals a similar average compared to all of 2018, with a slightly higher percentage of both emails and malware samples. See Table 2 for details.

Year MyDoom emails Total emails with malware % of MyDoom emails MyDoom samples Total malware samples % of MyDoom samples Jan-Jun 2019 465,896 41,002,585 1.1% 92,932 302,820 30.1%

Table 2. MyDoom statistics in the first six months of 2019.

Image 5. MyDoom activity levels in the first six months of 2019.

574 MyDoom samples appeared across more than one month, so the total number of MyDoom malware samples in Table 3 below is different than the total of MyDoom samples in the six-month period taken as a whole in the previous table.

Month MyDoom emails MyDoom malware samples Jan 2019 54,371 14,441 Feb 2019 47,748 11,566 Mar 2019 80,537 18,789 Apr 2019 92,049 17,278 May 2019 113,037 15,586 Jun 2019 78,154 15,846

Table 3. MyDoom month to month statistics in the first six months of 2019.

Image 6. Graph charting MyDoom activity from January through June of 2019.

Where have these emails come from? IP addresses of the top ten countries we saw during the first six months of 2019 were:

China: 349,454 emails

United States: 18,590 emails

Great Britain: 10,151 emails

Vietnam: 4,426 emails

Republic of Korea (South Korea): 2,575 emails

Spain: 2,154 emails

Russia: 1,007 emails

India: 657 emails

Taiwan: 536 emails

Kazakhstan: 388 emails

Image 7. Countries that MyDoom emails have appeared from during the first six months of 2019.

Targeted countries were more varied and evenly distributed than the source countries. Top ten targeted countries were:

China: 72,713 emails

United States: 56,135 emails

Taiwan: 5,628 emails

Germany: 5,503 emails

Japan: 5,105 emails

Singapore: 3,097 emails

Republic of Korea: 1,892 emails

Romania: 1,651 emails

Australia: 1,295 emails

Great Britain: 1,187 emails

Image 8. Targeted countries of MyDoom emails during the first six months of 2019.

The top ten verticals hit during this period were:

High Tech: 212,641 emails

Wholesale and Retail: 84,996 emails

Healthcare: 49,782 emails

Education: 37,961 emails

Manufacturing: 32,429 emails

Professional and Legal Services: 19,401 emails

Telecommunications: 4,125 emails

Finance: 2,259 emails

Transportation and Logistics: 1,595 emails

Insurance: 796 emails

These results are skewed likely towards our customer base. However, this data indicates that China and the United States are the source of most MyDoom emails and rank highest as the most targeted countries.

Characteristics of MyDoom

MyDoom distribution has had similar characteristics for years now. In February 2019, Cylance analyzed a sample of MyDoom, and current MyDoom samples follow similar characteristics. Emails distributing MyDoom are generally disguised as reports that an email was not delivered, with subject lines such as:

Delivery failed

Delivery reports about your e-mail

Mail System Error – Returned Mail

MESSAGE COULD NOT BE DELIVERED

RETURNED MAIL: DATA FORMAT ERROR

Returned mail: see transcript for details

However, we also frequently see MyDoom emails with random alphabetic characters in the subject line. MyDoom emails also use other subject lines like:

Click me baby, one more time

hello

Hi

say helo to my litl friend

Figures 8, 9, and 10 show screenshots of MyDoom email samples from July 2019.

Figure 8. Example of a MyDoom email from July 2019 (1 of 3).

Figure 9. Example of a MyDoom email from July 2019 (2 of 3).

Figure 10. Example of a MyDoom email from July 2019 (3 of 3).

Attachments from these MyDoom emails are executable files, or they are zip archives that contain executable files. MyDoom malware turns an infected Windows host into a malicious spambot, which then sends MyDoom emails to various email addresses. This will happen even if the infected Windows host does not have a mail client. Another characteristic of MyDoom is attempted connections to various IP addresses over TCP port 1042.

Figure 11. Emails traffic from a host infected with MyDoom on July 15th, 2019.

Figure 12. Attempted connections over TCP port 1042 from a host infected with MyDoom.

On a Windows 7 host, MyDoom makes a copy of itself in the user’s AppData\Local\Temp directory as lsass.exe, but the malware is not made persistent in the Windows registry. On a Windows XP host, the MyDoom executable makes a copy of itself at C:\Windows\lsass.exe and is made persistent through the Windows registry in the HKEY_LOCAL_MACHINE hive with a key named Traybar at SOFTWARE\Microsoft\Windows\CurrentVersion\Run as shown in Figure 13.

Figure 13. MyDoom persistent on a Windows XP host.

Conclusion

First seen in 2004, MyDoom is still active today– a testament to its original destructiveness. Enough infrastructure has remained infected throughout the years that we continue to see MyDoom in today’s threat landscape. Although a relatively small percentage of malware-based emails contain MyDoom, this malware remains a constant presence.

Based on our data, MyDoom-infected infrastructure resides at IP addresses mostly belonging to China, with the United States running a distant second. Both China and the United States are the primary recipients of MyDoom emails, although the distribution remains global and targets many other countries. High tech is the most frequently targeted industry.

Palo Alto Networks customers are protected from MyDoom by our threat prevention platform which easily detects this malware. AutoFocus users can track MyDoom attempts by using the MyDoom tag.

Palo Alto Networks has shared our findings, including file samples and indicators of compromise, in this report with our fellow Cyber Threat Alliance members. CTA members use this intelligence to rapidly deploy protections to their customers and to systematically disrupt malicious cyber actors. For more information on the Cyber Threat Alliance, visit www.cyberthreatalliance.org.

Indicators of Compromise

MyDoom EXE Samples from July 2019

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