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 SubjectAttachment
A/R Invoice – 1058071AR Invoice – 1058071.htm
FW: Documents? INVOICE AND STATEMENTDocuments.htm
DHL COPYSHIPMENT.html
FW: Purchase OrderQuote.html
Invoice ConfirmationInvoice (1).html
INVOICEINVOICE.html
P.O9035 Payment for ***.com: Wednesday, November 23, 2022OptoSort_GmbH_P.O24365.html
Payment Advise – Thursday, November 24, 2022ian.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 paymentInvoice settlement.shtml

Case: Malware (Infostealer, Downloader, etc.)

Email SubjectAttachment
Balanced payment for invoice 058418image004.img
BL-CTLT02060001967EA808465.IMG
DHL Shipment Notification 4816 Custom Form ECUSTOM CLEARNCE FORM E.xls
Inquiry HA-22-28199 22-077 for Mongolian MarketInquiry HA-22-28199 22-077,pdf.img
Inquiry HA-22-28199 22-077 for Mongolian MarketInquiry HA-22-28199 22-077.xls
New PO-SO210014-024New PO-SO210014-024.xls
orderQuote_2200001679.img
RE NYP6109212022NYP610921.ISO
Re GRAFINGER-ORDERGrafinger-CVE2-530334.iso
Re New Order 87012NEW ORDER 87012_PDF.IMG
RE PO1232451PO1232451.xls
RE REVISED ORDER CONFIRMATIONPURCHASE.ORDER.IMG
Re Transferencia PAGO TTTransferencia.pdf.img
REBBND List as on dt.18112022_20221118_2129.emlBBND.IMG
REQUEST FOR QUOTATION Ref. # IRQ2107778RFQ Ref. # IRQ2107778.img
Send email Invoice_0479.18.11.2022Invoice_0479.18.11.2022.img
Re[2]: very sexy images only for youwild__plp.exe
sexy picturessuperimg.jpg.exe
super wonderful picture don’t showsex-act.exe
orderQuote_2200001679.img
RE: MW90_CRF Port Klang_HongKong Taisung Innovase Enterprise Co. LtdMW90 CRF Port Klang_HongKong Taisung Innovase Enterprise Co. Ltd.r07
URGENT_RFQSPASHEET1.rar
URGENT RESPONSERFQEXCEL1.rar
RFQ23.11.202223112022Sheet01.rar
RE: NEW CONTRACT NO. 002/PPI/2/INV22100401PPI_002_TUMINH_SIGNED_pdf.rar
PaymentPayment Copy.rar
Kindly Quote itemsRFQ002511.rar
Kindly Quote itemsSheet001ESMPC1125.rar
TNT Express Invoice: 09004105 – Account: 000011320TNT Invoice_pdf.xz
SAMPLE FOR REQUESTTESN REQUEST SAMPLE.z
Fwd: REMITTANCESREMITTANCE COPY – Nov 2022.zip
New Shipment notificeSHIPPING DOC.zip
Arrange balance paymentProof of payment.zip
DHL AWB – 4520065422DHL AWB – 4520065422_Nov.2022.zip
Fwd: AW: Re: REMITTANCESREMITTANCE COPY#900024415xxxx2022.zip
NEW DECEMBER ORDER PO#137810205NEW_ORDER_PO137810205.pdf.zip
BANK DETAILS CONFIRMATIONswift(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.

Fake Login Page (FakePage) C2 URL

When users enter their IDs and passwords on the fake login page 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://formspree.io/f/xwkzwzdj
  • hxxps://exptools.com.sg/PDF-NEW.php
  • hxxp://zena.med.br/wp-includes/assets/post.php
  • hxxps://chrismassseasons.xyz/aaaloll/anydomain.php
  • hxxps://pilasterlllc.com/neo/wp-confort.php
  • hxxps://emsrvs-centers.tk/mrk309028oyustered/response/zender.php
  • hxxps://submit-form.com/KezvKLLz
  • hxxps://submit-form.com/CeQwEXsb
  • hxxps://submit-form.com/GMp7u0F8

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])

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