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 June 4th, 2023 to June 10th, 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.
During this week, the most prevalent threat type seen in phishing email attachments was Downloader with 37%. Downloaders downloaded various additional malware such as Infostealers and backdoors. The second most prevalent type was Infostealers (29%) like AgentTesla, FormBook, and AveMaria, that leak user credentials saved in web browsers, emails, and FTP clients. It was then followed by FakePages (18%), which 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 those mentioned above, Trojan (15%) and Exploit (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. FakePages were distributed through web pages script (HTM, HTML, SHTM, SHTML) documents that must be executed with a web browser. Other malware, including Infostealer and downloader, came attached to emails with file extensions including compressed files (RAR, Z, GZ, 7Z, etc.).
Cases of Distribution
The following are distribution cases that occurred during the week from June 4th, 2023 to June 10th, 2022. 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 identical English subject and texts.
|[FedEx] Tariffs payment notice (Tax Invoice)||Tax_Notification.html|
|[Korean Air Shipment] Clearance of original invoices and packing lists.||Original-invoice_lee_********.htm|
|DHL Invoice & Delivery Arrival Document (ARRIVAL NOTICE)||DHL AWB_INV.shtm|
|[DHL] Notice on Import Tax Payment Deadline – (INV and AWB) ✈||DHL SCANNED ORIGINAL DOC.htm|
|Come on, quickly withdraw your +25,176$! The account is not blocked yet||Your_accounts_with_a_balance_of_27125%24_will_be_blocked-2183.pdf|
|Invoice, PI, bill of lading (shipping documents)||FedEx Import Tax Invoice.html|
|Action Required: Your Account Requires Verifying Some Information||american express-mail-security.html|
|An Urgent Review Requires Your Attention Immediately||wellsfargo-account-protection-alerts.html|
|You have 24 hours to withdraw +23.536$||The_main_thing_is_to_have_time_to_withdraw_your_15494%24-8235.pdf|
|RE: TR: Fuite dossier FILLAT||P.pdf|
|NEW ORDER (PO9924RHN43)||PO1124RHN43.html|
|+14,857$ will be cancelled in 24 hours||Come_on%2C_quickly_withdraw_your_21778%24_The_account_is_not_blocked_yet-12459.pdf|
|You have a New Message||USAA NEW DOCUMENT.pdf|
|JUNE P.O _3000000821||JUNE P.O _3000000821.Shtm|
|Your account already has +19,741$||21%2C731%24_burn_out_in_24_hours-4259.pdf|
|Shipment Booking Confirmation – Bill of Lading Document – Original Scan copies of Document||Scanned Copies of Packing List_ETD.Pdf.htm|
|DHL AWB 到货通知#310479442||DHL AWB#310479442.html|
|INVOICE & SHIPMENT – 9 Jun 2023||dhl-shipment_invoice PI-Bill Of Lading#998454.htm|
|Cosmax USA PO# 4500926140||PO#4500926140 & #0018288.pdf.html|
|FW:ATTACHED SWIFT COPY 6/9/2023 2:33:49 p.m.||AWDPAYMENT-RECEIPT.html|
Case: Malware (Infostealer, Downloader, etc.)
|This is a digital (tax) bill sent and issued by the National Tax Service Hometax||NTS_eTaxInvoice·pdf.zip|
|Quotation Request||Request for Quotation.7z|
|Tax Invoice – [DHL] Acceptance of Import Declaration (Payment Before Acceptance)||Tax Invoice.rar|
|Pending DHL Shipment Notification REF: 02/6/2023||Shipping doc.img|
|Re: New Order PO# DTD28102022 (SO# 11280).||Re New Order PO# DTD28102022 (SO# 11280)..rar|
|Shipment Delivery Address *(Required) contact form||Shipment Delivery Address.rar|
|Management Review and the IQMP Compact Checklist -IQMP DP571911277||scan16431643.zip|
|FWD: PAYMENT SWIFT||ISLAMIC BANK SWIFT.pdf.z.rar|
|Balance Payment – 06062023||06062023_8091526433_0010017265.gz|
|Fwd: New enquiry||E700 quotation20111209.r09|
|RE: New Shipment Order / Urgent Request Approval of Draft Shipping Docs (BL/SZOE23050007)||DOCS.r15|
|Arrange balance payment||bank SWIFT massage.rar|
|Fw: Outstanding Payment||Payment Advice – 8243001970.gz|
|New Purchase order sanseo.shop||Purchase Order 2023.0608.pdf.z|
|New PO(Trial) – 230102||PSC_ A-2303310.rar|
|LIABILITY POLICY, 07/01/2023 – 07/01/2024 NM89515177||scan18871887.zip|
|RE: SWIFT & ADVICE – BALANCE AMT PAID —-IMP NO. 31/23-24||Transaction receipt.xls|
|Re: RE : New Order_PO234||PO450.ISO|
|New Purchase order (J.Global) no. 155362-A||NEW_PO155362A_JGlobal_Pdf.rar|
|New enquiry||40023540MES_S Quote.img|
|FW:Saudi Aramco.co//ENQ-0090/F/8||Saudi AramcoENQ-0090F8.PDF.r02|
|RE: Confirm revised invoice to proceed with payment ASAP||payment invoice-pdf.gz|
|DHL Express Awb no: 2284285290 Información de declaración de microexportación||2284285290 ETGB_IHRACAT.7z|
|Purchase Order No 1600064995 _ 00000000||Purchase Order No 1600064995 _ 00000000.pdf.GZ|
|RFQ of CFP Crude Oil Tank Project: 19P3792A-M11A.01A_Z1:(A/G)||Crude Oil Tank Project_General Spec.gz|
|Commercial Invoice and Bill Of Lading.||Bill Of Lading..rar|
|New Inquiry||New Inquiry.rar|
|5314 Statement 0013167791 for Remittance||5314 Statement 0013167791.zip|
|LOI/North Oil Company 6000003101||RFQ No. 6000003101.PDF.z|
|RE: RE:Sonak Corporation new Order||FOB $Corporation new OrderPDF.r00|
|RE: RFQ-Huada Superabrasive Tool Technology Co., Ltd||RE RFQ-Huada Superabrasive Tool Technology Co., Ltd00PDF.r00|
|RE: BOOOKING PAYMENT||Booking_826111pdf.7z|
|PO FOR SC310962Z105||SC310962ZI05.IMG|
|Express Delivery Arrival Notification attached #3178 June 2023||Shipment Delivery Notification and Release Documents.img|
|DHL Express – the commercial invoice 2898435030 157662876374||Commercial_CVS_inv.03.04.2017.zip|
|OOCL Arrival Notice At Final Destination: OOLU4051770254 | COSCO SHIPPING ANDES – 017E||BL2716915060623.PDF.r00|
|New Order||NEW PO – 4610926543.gz|
|RE: HOLIDAY TOURS REQUEST||Booking_07_10623pdf.7z|
|Dhl Notification for shipment||DHL – COMMERCIAL INVOICE, BILL OF LADING, ETC_DOC.gz|
|DHL AWB – 5032675892||DHL AWB 5032675892.gz|
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: ‘Hometax Tax Bill’
The keywords for this week are ‘Hometax Tax Bill’. May is the month of filing the general income tax in Korea. Following this, the threat actor impersonated the National Tax Service to distribute the GuLoader malware to multiple normal users. Inside the attached compressed file “NTS_eTaxInvoice-pdf.zip” is an EXE-type GuLoader with the same file name. This malware is a downloader that additionally downloads a backdoor or an Infostealer. At the time of analysis, the NanoCore RAT tool was downloaded, and the threat actor can take remote control of user PCs with this tool. As such, when opening attachments in emails, users must check their sources and be cautious of opening executable files such as those with the EXE extension.
NTS_eTaxInvoice-pdf.exe (ED9A4BBACD25426E9403E7847619F5BE) V3 file detection information/engine version – Trojan/Win.GuLoader.R585076 (2023.06.07.02)
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.
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)
- Phishing (Initial Access, ID: TI1566)
- Internal Spearphishing (Lateral Movement, ID: T1534)
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