ASEC Weekly Phishing Email Threat Trends (November 20th, 2022 – November 26th, 2022)

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 November 20th, 2022 to November 26th, 2022 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. Additionally, the type that leaks login account credentials will be defined as FakePage.

Phishing Emails

During this week, the most prevalent threat type seen in phishing email attachments was Infostealer, taking up 34%. 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 fake login pages (FakePage), which took up 21%. FakePages 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.^{See <Fake Login Page C2> below}

Aside from these, Trojan (15%), Backdoor (10%), Worm (8%), Downloader (7%), 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>.

File Extensions in Phishing Emails

We have identified which file extensions were used by the threats above for the distribution of email attachments. As FakePages 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, R07, 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 the distribution cases that occurred during the week from November 20th, 2022, to November 26th, 2022. 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: Fake Login Pages (FakePage)

Email Subject	Attachment
A/R Invoice – 1058071	AR Invoice – 1058071.htm
FW: Documents? INVOICE AND STATEMENT	Documents.htm
DHL COPY	SHIPMENT.html
FW: Purchase Order	Quote.html
Invoice Confirmation	Invoice (1).html
INVOICE	INVOICE.html
P.O9035 Payment for ***.com: Wednesday, November 23, 2022	OptoSort_GmbH_P.O24365.html
Payment Advise – Thursday, November 24, 2022	ian.tolfree_Payment Schedule-PL-PG-19703507.file.html
Re: Re: Request of Quotation.	new-order P.o.html
Your mailbox is 98% full.	Storage Settings.html
Fwd: attached invoice for balance payment	Invoice settlement.shtml

Case: Malware (Infostealer, Downloader, etc.)

Email Subject	Attachment
Balanced payment for invoice 058418	image004.img
BL-CTLT02060001967	EA808465.IMG
DHL Shipment Notification 4816 Custom Form E	CUSTOM CLEARNCE FORM E.xls
Inquiry HA-22-28199 22-077 for Mongolian Market	Inquiry HA-22-28199 22-077,pdf.img
Inquiry HA-22-28199 22-077 for Mongolian Market	Inquiry HA-22-28199 22-077.xls
New PO-SO210014-024	New PO-SO210014-024.xls
order	Quote_2200001679.img
RE NYP6109212022	NYP610921.ISO
Re GRAFINGER-ORDER	Grafinger-CVE2-530334.iso
Re New Order 87012	NEW ORDER 87012_PDF.IMG
RE PO1232451	PO1232451.xls
RE REVISED ORDER CONFIRMATION	PURCHASE.ORDER.IMG
Re Transferencia PAGO TT	Transferencia.pdf.img
REBBND List as on dt.18112022_20221118_2129.eml	BBND.IMG
REQUEST FOR QUOTATION Ref. # IRQ2107778	RFQ Ref. # IRQ2107778.img
Send email Invoice_0479.18.11.2022	Invoice_0479.18.11.2022.img
Re[2]: very sexy images only for you	wild__plp.exe
sexy pictures	superimg.jpg.exe
super wonderful picture don’t show	sex-act.exe
order	Quote_2200001679.img
RE: MW90_CRF Port Klang_HongKong Taisung Innovase Enterprise Co. Ltd	MW90 CRF Port Klang_HongKong Taisung Innovase Enterprise Co. Ltd.r07
URGENT_RFQ	SPASHEET1.rar
URGENT RESPONSE	RFQEXCEL1.rar
RFQ23.11.2022	23112022Sheet01.rar
RE: NEW CONTRACT NO. 002/PPI/2/INV22100401	PPI_002_TUMINH_SIGNED_pdf.rar
Payment	Payment Copy.rar
Kindly Quote items	RFQ002511.rar
Kindly Quote items	Sheet001ESMPC1125.rar
TNT Express Invoice: 09004105 – Account: 000011320	TNT Invoice_pdf.xz
SAMPLE FOR REQUEST	TESN REQUEST SAMPLE.z
Fwd: REMITTANCES	REMITTANCE COPY – Nov 2022.zip
New Shipment notifice	SHIPPING DOC.zip
Arrange balance payment	Proof of payment.zip
DHL AWB – 4520065422	DHL AWB – 4520065422_Nov.2022.zip
Fwd: AW: Re: REMITTANCES	REMITTANCE COPY#900024415xxxx2022.zip
NEW DECEMBER ORDER PO#137810205	NEW_ORDER_PO137810205.pdf.zip
BANK DETAILS CONFIRMATION	swift(USD 17043.50).zip

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

Keywords to Beware of: ‘Payment’, ‘Invoice’

There were multiple malicious emails that disguised themselves as having been sent from certain companies by using transaction-related keywords such as ‘invoice‘ and ‘payment.’ The email below is attached with an IMG file named ‘image004.img.’ Disk image files (IMG) are the most widely distributed type at the moment, and they have a malicious executable inside, which is PureCrypter malware classified as a downloader.

 

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. 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 antivirus 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])

 

URL

http[:]//zena[.]med[.]br/wp-includes/assets/post[.]php

https[:]//chrismassseasons[.]xyz/aaaloll/anydomain[.]php

https[:]//emsrvs-centers[.]tk/mrk309028oyustered/response/zender[.]php

https[:]//exptools[.]com[.]sg/PDF-NEW[.]php

https[:]//formspree[.]io/f/xwkzwzdj