ASEC Weekly Phishing Email Threat Trends (November 13th, 2022 – November 19th, 2022 )

The ASEC analysis team monitors phishing email threats with the ASEC automatic analysis system (RAPIT) and Honeypot. This post will cover the cases of distribution of phishing emails during the week from November 13th, 2022 to November 19th, 2022 and provide statistical information on each type. Additionally, we will introduce new types that were not detected before as well as emails to be cautious of with keywords to minimize harm to users. The phishing emails covered in this post will only be those that have attachments. Emails that have malicious links in the body without attachments will be excluded.

Phishing Emails

During this week, the most prevalent threat type seen in phishing email attachments was Infostealer (29%). Infostealer includes AgentTesla and FormBook, where it steals user credentials saved in web browsers, emails, and FTP clients.

Then, it was followed by downloader (28%), which includes loaders such as SmokeLoader and GuLoader, and then by fake login pages (FakePage, 26%). Fake login pages are web pages where the threat actor has imitated the screen layout, logo, and font of the real website, leading users to enter their account and password information. The input information is sent to the threat actor’s C2 server.^{Refer to <Fake Login Page C2> below}

Aside from these, Trojan (8%), Backdoor (5%), Worm (2%), and Exploit (2%) types were detected. The threat types using phishing email attachments and their order of prevalence are similar to the order of malware distribution published weekly in the <ASEC Weekly Malware Statistics>. This shows us that phishing emails (ID: T1566^[1]) used in the attack’s initial access (ID: TA0001^[2]) affects the overall malware distribution.

File Extensions in Phishing Emails

We have checked which file extensions were used by the threats above for the distribution of email attachments. As fake login pages are web page scripts that must be executed with a web browser, they were distributed with HTML, SHTML, and HTM file extensions. Other malware, including Infostealer and downloader, came attached to emails with various file extensions including compressed files (ZIP, R00, GZ, RAR, XZ, etc.), IMG disk image files, and XLS document files. With the exception of fake login pages which have to be web page script files, other malware were distributed with a variety of file extensions regardless of the threat type.

Cases of Distribution

The following are distribution cases that occurred during the week from November 13th, 2022 to November 19, 2022. The cases will be classified into fake login pages and malware types, including Infostealer, Downloader, Exploit, and Backdoor. The numbers that appear on email subjects and in the attachment file names are generally unique ID values, and they can differ according to the email recipient. Distribution cases with Korean subjects were also found; These are cases that specifically targeted Korean users instead of propagating themselves globally using the same English subject and text.

Case: Fake Login Pages (FakePage)

Case: Malware (Infostealer, Downloader, etc.)

The ASEC analysis team has selected keywords that users must look out for, based on the distribution cases above. If these keywords are included in the subject of the email, or if the same characteristics are found, users must exercise strict caution as they may be phishing emails from threat actors.

Keyword to Beware of: ‘Payment Copy‘

This was included in Korean email subjects, where the sender was masquerading as an employee of a company. It attempted to deceive users with content about a ‘payment copy’ and was attached with a fake login page, “Payment Copy.html”. When the attachment is executed, a page is loaded and prompted the user to log in to their mailbox to view the Excel file online.

Keyword to Beware of: Uncommon File Extensions (‘UUE’, ‘R00’, ‘XZ’, ‘BZ2’) on Attachments

Malware were also distributed as compressed files with quite uncommon file extensions such as ‘UUE’, ‘R00’, ‘XZ’, and ‘BZ2’. The case below shows an attachment with the UUE file extension with the filename, “Inquiry #140220.pdf.UUE”. This UUE file is actually a RAR compressed file and includes a malicious EXE executable. The executable inside is AgentTesla, a type of Infostealer.

Fake Login Page (FakePage) C2 URL

If a user enters their account and password into the fake login page created by the threat actor, the information is sent to the threat actor’s server. The list below shows the threat actor’s C2 addresses of fake login pages distributed during the week.

• hxxps://formspree.io/f/xwkzwzdj
• hxxps://submit-form.com/7Qhdye4M
• hxxps://vladiolitrade.ru/coc/zender.php
• hxxp://hybridpro.com/mailb_fix.php
• hxxps://multiservicon.com/wp-ra/adbn.php
• hxxps://strofima.com/pdf.php
• hxxps://hoellooooo.ga/Esp/sharepoint.php
• hxxps://tech4herafrica.com/wp-includes/dri/Drbox001.php

Preventing Phishing Email Attacks

Attacks using phishing emails are disguised with content that can easily deceive users, such as invoices and tax payments, to induce users to access fake login pages or execute malware. FakePages are evolving more over time to closely resemble the original pages. Malware are packed into compressed file formats, bypassing the attachment scans of security software. Users must practice strict caution and refer to recent cases of distribution to avoid being exposed to infection by malicious phishing emails. The ASEC analysis team advises the following email security measures.

• Links or attachments in emails from unverified senders must not be executed until proven to be credible.
• Sensitive information such as login account credentials must not be entered until the place of input can be trusted.
• Attachments with unfamiliar file extensions must not be executed until they can be trusted.
• Security products including antivirus software must be used.

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