Email Threat Review May 2022

Summary

In this monthly email threat review installment, we present an overview of the email-based threats observed in May 2022 and compare them to the previous month’s threats.

The report provides insights into:

• Unwanted emails by category
• File types used in attacks
• Industry Email Threat Index
• Attack techniques
• Impersonated company brands and organizations

Unwanted emails by category

The following table shows the distribution of unwanted emails per category.

Email category	%
Rejected	81.81
Spam	13.45
Threat	3.85
AdvThreat	0.85
Content	0.04

The following histogram shows the email volume per category per day.

Methodology

The listed email categories correspond to the email categories listed in the Email Live Tracking of Hornetsecurity’s Control Panel. So our users are already familiar with them. For others, the categories are:

Category	Description
Spam	These emails are unwanted and are often promotional or fraudulent. The emails are sent simultaneously to a large number of recipients.
Content	These emails have an invalid attachment. The administrators define in the Content Control module which attachments are invalid.
Threat	These emails contain harmful content, such as malicious attachments or links, or they are sent to commit crimes like phishing.
AdvThreat	Advanced Threat Protection has detected a threat in these emails. The emails are used for illegal purposes and involve sophisticated technical means that can only be fended off using advanced dynamic procedures.
Rejected	Our email server rejects these emails directly during the SMTP dialog because of external characteristics, such as the sender’s identity, and the emails are not analyzed further.

File types used in attacks

The following table shows the distribution of file types used in attacks.

File type (used in malicious emails)	%
Archive	33.8
HTML	17.0
PDF	16.4
Excel	13.7
Executable	5.8
Other	5.6
Disk image files	4.7
Word	1.7
Script file	0.6
Email	0.4
LNK file	0.3

The following histogram shows the email volume per file type used in attacks per 7 days.

Industry Email Threat Index

The following table shows our Industry Email Threat Index calculated based on the number of threat emails compared to each industry’s clean emails (in median).

Industries	Share of threat in threat and clean emails
Research industry	7.0
Manufacturing industry	4.4
Automotive industry	4.3
Media industry	4.0
Mining industry	4.0
Utilities	4.0
Education industry	3.8
Healthcare industry	3.7
Transport industry	3.7
Construction industry	3.6

The following bar chart visualizes the email-based threat posed to each industry.

This month saw an increased threat index for the research industry. Other industries display a slightly relaxed threat index compared to the previous month.

Methodology

Different (sized) organizations receive a different absolute number of emails. Thus, we calculate the percent share of threat emails from each organization’s threat and clean emails to compare organizations. We then calculate the median of these percent values for all organizations within the same industry to form the industry’s final threat score.

Attack techniques

The following table shows the attack techniques used in attacks.

Attack technique	%
Phishing	40.0
URL	14.9
Advance-fee scam	7.8
Executable in archive/disk-image	4.3
Extortion	4.0
Impersonation	2.0
Maldoc	1.4
HTML	1.3
PDF	0.3
Other	23.9

The following histogram shows the email volume per attack technique used per hour.

Impersonated company brands and organizations

The following table shows which company brands and organizations our systems detected most in impersonation attacks.

Impersonated brand or organization	%
Sparkasse	60.9
Amazon	7.6
DHL	5.6
UPS	2.1
Dropbox	1.6
Microsoft	1.5
Netflix	1.4
LinkedIn	1.4
Fedex	1.2
Volks- und Raiffeisenbank	1.1
1&1	1.0
Postbank	1.0
Other	13.6

The following histogram shows the email volume for brands and organizations detected in impersonation attacks per hour.

Although we observed some pauses in the ongoing Sparkasse phishing campaigns, Sparkasse still dominates our charts. Sparkasse is a German public bank.