ASEC Weekly Phishing Email Threat Trends (March 12th, 2023 – March 18th, 2023)

AhnLab Security Emergency response Center (ASEC) 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 March 12th, 2023 to March 18th, 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 FakePage with 66%. 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} The second most prevalent threat type was Downloader (10%), which includes loaders such as SmokeLoader and GuLoader. It was then followed by Trojan (7%) and Infostealers (7%) like AgentTesla and FormBook that leak user credentials saved in web browsers, emails, and FTP clients. The .NET packer makes up most of Trojan, and this has been introduced in the previous blog post ‘Types of Recent .NET Packers and Their Distribution Trends in Korea‘ as Type 3 ‘VariantCrypter’. Aside from those mentioned above, Worm (6%) and Exploit (4%) 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. FakePages were distributed through web pages script (HTML, HTM, SHTML) documents 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 (ZIP, R09, RAR), IMG disk image files, and PDF document files. One thing to note for this week is that a VHDX extension format was reported.

Cases of Distribution

The following are distribution cases that occurred during the week from March 12th, 2023 to March 18th, 2023. The cases will be classified into FakePage 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

Email Subject	Attachment
New DHL Shipment Document Arrival Notice / Shipping Documents / Original BL, Invoice & Packing List	(DHL) Original BL, PL, CI Copies.htm
FedEx Shipment Arrival Notice	AWB#989345874598.html
Hyundai: 견적 요청/ PO #10487X6	Quotation Request PO #10487X65.htm
FedEx Shipment Notice of arrival	OFFICE #.html
NEW FAX 13 Mar 2023	Quotation Request Scan_PO #1192-ID_HYU-23.htm
Re: Quotation Request PO #1192-ID_HYU-23 (Project )	***.com_SI0284627_pdf.shtml
Kindly Check Company Bank Information	Shipping_Doc.html
[FedEx 814709668979] Your package has arrived	FedExParcelShipment.html
Signed Documents	Doc_____________j****e@a***d*.co.kr.HTM
ENC: RES: ENC: APARELHO COM DEFEITO_PROBLEMAS COM REPARO/SOLU	Quis.html
EFT Payment sent On: Monday, March 13, 2023 3:57 p.m.	ruizhen02 Voucher.shtml
PO 10120H5 (Invoice Request)	PO 10120H5Purchase Order.htm
New Order- Medical Oem Ref#: 20-1939A – I-SENS	Purchase Order RFQ List.pdf
Re: PO NO. PO-O3465-0001 // ORDER INV-O34652726-PI	PO269007-SPL ORDER.pdf.htm
Pickup Confirmation Wednesday, March 15, 2023 5:2 a.m..	Swift_confirmation_copy.PDF.shtml
PO#2388	PO#2388___PDF.html
Re: PO 1015_INV (Invoice Request)	Invoice RequestPO 1015_INV.htm
Quotation Request	PO 230310-21A.htm
Truefriend You’ve received EFT For INV7098590870. Thu 3/16/23	ATT5098090870908.htm
Please_find_attached_Aging_Reports_for_Truefriend_arrive_on_March_15_2023_at_A11	TruefriendStatement.HTM
EFT Payment sent On: Monday, March 13, 2023 4:51 p.m.	entec Voucher.shtml
Debt Recovery: Legal Action For Unpaid Invoices.	Debt_Recovery_Suit_&_Invoices_2022_2023.hTm
Fwd: New Quote needed for the attached document	Quote Project-#2 *******@t*******d.com PDF.html
Your parcel has arrived urgent pick up needed today.	copy.AWB #0675854897.htm
New Order- Ref#: 20-1939A – I-Sens	Purchase Order_PDF.html
R.F.Q_PURCHASE-ORDER	PURCHASE ORDER.html
Account Suspension	Update Account.html
[DHL#003791-748294] Your package has arrived	DHLParcelShipment.html
Re:FedEx Logistic收到货件通知	Invoice. AWB#84248_pdf.htm
(INV and AWB/PACKING LIST) Your DHL Parcel Has Arrived	ParcelDocumentDHL.html

Case: Malware (Infostealer, Downloader, etc.)

Keywords to Beware of: ‘Acceptance of Import Declaration’

[Figure] A large number of emails being distributed with ‘Acceptance of Import Declaration’ as the subject

[Figure] vbs malware (Guloader) inside the attached compressed file

• 

  [Figure] A portion of the attached VBS (Tax Notification-7759303436.vbs) code

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.

• https[:]//formspree[.]io/f/xdovzjlo
• https[:]//submit-form[.]com/OIIpXOTl
• https[:]//daca[.]hostedwebsitesystem[.]com/vendor/phpunit/phpunit/src/Util/Log/index/index/spam/FedExpress[.]php
• https[:]//formspree[.]io/f/mjvdynwp
• https[:]//formspree[.]io/f/xwkjbjgo
• https[:]//formspree[.]io/f/myyakjqr
• http[:]//martinamilligan[.]co[.]business/ono/fdx[.]php
• https[:]//clinicacarlosgomes[.]med[.]br/wp-admin/kal/fte(1)[.]php
• https[:]//formspree[.]io/f/mzbqgqyp
• https[:]//mallarg[.]tk/lp/fte[.]php
• https[:]//seafordrotary[.]org[.]au/Eppdff[.]php
• https[:]//k2-server[.]duckdns[.]org/roundbuk/pdf[.]php
• https[:]//cupertinochiropracticcenter[.]com/index/FedExpress[.]php
• https[:]//zenkoren[.]itigo[.]jp//cgi-bin/123/cloudlog[.]php
• https[:]//huntingfieldlodge[.]com[.]au/Aa/Excel22[.]php
• https[:]//formspree[.]io/f/mnqyznyy
• https[:]//mgffomento[.]com[.]br/wp-admin/dd/postdhll[.]php
• https[:]//holisticfacades[.]com[.]ng/wp-includes/aa/feed[.]php
• https[:]//dissertational-spee[.]000webhostapp[.]com/wp-admin/purchase/pdf[.]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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