ASEC Weekly Phishing Email Threat Trends (January 29th, 2023 – February 4th, 2023)

The ASEC analysis team monitors phishing email threats with the ASEC automatic sample analysis system (RAPIT) and honeypot. This post will cover the cases of distribution of phishing emails during the week from January 29th, 2023 to February 4th, 2023 and provide statistical information on each type. Generally, phishing is cited as an attack that leaks users’ login account credentials by disguising as or impersonating an institute, company, or individual through social engineering methods. On a broader note, the act is a technical subterfuge that enables the threat actor to perform attacks such as information leaks, malware distribution, and fraud against various targets. The focus of this post will be on the fact that phishing attacks mainly occur through emails. We will also provide a detailed classification of various attack methods that are based on phishing emails. Furthermore, we will make an effort to minimize user damage by introducing new attack types that have never been found before and emails that require users’ caution, along with their keywords. 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, taking up 39%. Infostealer includes malware such as AgentTesla and FormBook, and they leak user credentials saved in web browsers, emails, and FTP clients. It was then followed by FakePage, which took up 36%. FakePages are web pages where the threat actor has imitated the screen layout, logo, and font of the real login pages or advertising pages, leading users to enter their account and password information. The input information is sent to the threat actor’s C2 server or used to induce users to access other fake websites. ^{See <FakePage C2> below} Aside from these, Downloader (9%), Exploit (4%), Trojan (4%), Worm (4%), Backdoor (2%), and Dropper (1%) 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>.

File Extensions in Phishing Emails

We have identified which file extensions were used by the threats above for the distribution of email attachments.  Among the phishing email attachment types, the ONE extension (4%) is notable for its continuous distribution. OneNote is a digital note-taking application developed by Microsoft, which allows users to insert content anywhere on the pages unlike word processing programs. FakePages were distributed with PDF documents or web pages scripts (HTML, SHTML, HTM) that must be executed with a web browser. Other malware, including Infostealer and downloader, came attached to emails with various file extensions including compressed files (GZ, ZIP, RAR, R00, R15, R17), disk image files (IMG), and document files (ONE, XLS, XLSX, PDF). With the exception of FakePages that are distributed through web pages script files (HTML, HTM, SHTML) and PDFs, other malware types 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 January 29th, 2023 to February 4th, 2023. The cases will be classified into fake login pages and malware types, including Infostealer, Downloader, Exploit, and Backdoor. The numbers in email subjects and attachment filenames are unique IDs and may vary depending on 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 identical English subject and text.

Case: 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. 

Keywords to Beware of: ‘ONE‘

The keyword for this week is ‘ONE’, the extension of OneNote. Ever since the latest version of MS Office (Office 365) started using the policy of deactivating Office macro by default last year, there have been more and more malware strains that include the ONE extension. AsyncRAT, Qakbot, Redline, and AgentTesla are the main ones that are distributed via the ONE extension, and these malware strains have been covered in the Weekly Malware Statistics as well. As such, the team advises extra caution when executing attachments with the “ONE” extension in their emails.

FakePage C2 URL

When users enter their IDs and passwords on the login pages among the FakePages created by the threat actor, their information is sent to the attacker’s server. The list below shows the threat actor’s C2 addresses of fake login pages distributed during the week.

• hxxps://submit-form[.]com/QgFJw0n1
• hxxps://sagaschool.vip-saga.com[.]ua/wp-includes/zonic/newopo.php
• hxxps://newskoodai[.]com/press/bgLf4WBIDJaAjbgLf4WBIDJaAj
• hxxps://lifeushard[.]cyou/file.php
• hxxps://formspree[.]io/f/xdovnyrz
• hxxps://formspree[.]io/f/mgebolql
• hxxps://dearasia.bambooairways[.]com/wp-admin/inke/Macus_ssw.php
• hxxps://curriculums[.]cc/Xwery08/feedback.php
• hxxps://bkfkr.000webhostapp[.]com/kr/kr/act.php
• hxxp://charlesnewmarch.co[.]uk/wp-includes/4T4/mailform.php
• hxxp://benchmarkpk[.]com/wp-includes/@/cloudlog.php
• hxxp://accup.pluspluggg[.]com/mailb_fix.php

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. Fake login pages are evolving by the second to closely resemble the original pages. The attackers pack malware in compressed file formats to escape the attachment scans of users’ security products. 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 recommends users follow the email security guidelines below.

• Do not execute links and attachments in emails from unverified senders until they are proven to be credible.

• Do not enter sensitive information such as login account credentials until the site is found to be reliable.

• Do not execute attachments with unfamiliar file extensions until they are found to be reliable.

• Use security products such as antimalware software.

According to the MITRE ATT&CK framework, phishing email attacks correspond to the following techniques.

• Phishing for Information (Reconnaissance, ID: T1598^[1])

• Phishing (Initial Access, ID: TI1566^[2])

• Internal Spearphishing (Lateral Movement, ID: T1534^[3])

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