EXPLORE DETECTIONS
Attachment: QR code with encoded recipient targeting and redirect indicators
Detects QR codes in attachments that contain the recipient's email address (either plaintext or base64 encoded) and redirect through suspicious URI structures commonly associated with Kratos/SneakyLog redirection services.
Attachment: QR code with recipient targeting and special characters
Detects messages with QR code in attachments containing special characters in the path that include the recipient's email address in either the URL path or fragment, potentially encoded in base64. The URLs have a simple path structure and may end with suspicious patterns.
Attachment: QR code with suspicious URL patterns in EML file
Detects EML attachments containing QR codes that link to URLs with suspicious patterns, including specific alphanumeric combinations in subdomains and paths, or special characters followed by encoded terminators. These patterns are commonly used to evade detection in credential theft attacks.
Attachment: QR code with userinfo portion
Detects inbound messages that contain image or document attachments with QR codes containing embedded usernames, passwords, or excessively padded URLs. This technique is used to bypass traditional text-based detection methods.
Attachment: QuickBooks PDF lure
Detects inbound messages containing PDF attachments that match YARA signatures identifying QuickBooks-themed lure content.
Attachment: RDP connection file
Recursively scans files and archives to detect RDP connection files. Coercing a target user into connecting to an attacker-owned RDP server can expose elements of their host and potentially lead to compromise.
Attachment: RFC822 containing suspicious file sharing language with links from untrusted sender
This rule identifies messages with an RFC822 attachment contains language indicative of suspicious file-sharing activity. It checks both the original sender and the nested sender against highly trusted domains. The original message is unsolicited, and has not been previously flagged as a false positive.
Attachment: RFP/RFQ impersonating government entities
Attached RFP/RFQ impersonates a U.S. government department or entity to commit fraudulent transactions.
Attachment: Risk assessment PDF with inline image
Detects inbound messages containing a PDF attachment whose file name matches a 'risk assessment' naming pattern with an alphanumeric code, alongside an inline image attachment referenced via content ID in the HTML body. Messages from highly trusted sender domains that pass DMARC authentication are excluded.
Attachment: Romance scam with image lure and advance-fee or suspicious link indicators
Detects inbound messages that are not replies, forwards, or mailing list communications, and contain image attachments (JPG or PNG) alongside body text classified as romantic or sexually explicit in nature. The messages either include links to known redirector or free hosting domains (such as geno.link or sites.google.com), or exhibit advance-fee fraud intent while routing replies to a free email provider despite originating from a corporate-looking sender domain. Senders observed span spoofed government and business addresses as well as free webmail accounts, with subject lines using romantic or personal connection lures.
Attachment: RTF file with suspicious link
This rule detects RTF attachments directly attached or within an archive, containing an external link to a suspicious low reputation domain.
Attachment: RTF with embedded content
RTF files can contain embedded content similar to OLE files (Microsoft Office documents.)
Attachment: RTF with link to free-hosted Cloudflare Pages
Detects inbound emails that contain an RTF attachment. The rule extracts embedded content from the RTF file and inspects any URLs found within it, following redirects and analyzing the final destination page's links. It flags cases where those links point to domains hosted on the free Cloudflare Pages service (pages.dev), a common tactic used to host malicious or deceptive content while evading detection.
Attachment: Self-sender PDF with minimal content and view prompt
Detects messages where the sender and recipient are the same address with a PDF attachment containing only 'VIEW PDF' text and a standardized body message requesting to view the attachment.
Attachment: SFX archive containing commands
Attachment is an SFX archive that contains commands that will execute when opened. This can be used to run malicious commands, and has been observed in the wild.
Attachment: Single-page PDF with S3-hosted HTML link
Detects inbound messages containing a single-page PDF attachment that includes exactly one URL, which links directly to an HTML file hosted on an Amazon S3 bucket. This technique is commonly used to redirect recipients to credential harvesting pages while leveraging trusted cloud infrastructure to evade detection.
Attachment: Small text file with link containing recipient email address
Attach text file is less than 1000 bytes and contains a recipients email address. Seen in the wild carrying credential phishing links.
Attachment: Soda PDF producer with encryption themes
Detects an observed TTP of using Soda PDF (which offers a free trial) to produce PDFs which OCR output contains references to encryption and mentions a PDF. The PDF contains a single link which has been observed linking to a credential phishing page.
Attachment: Suspicious employee policy update document lure
Inbound message containing subject line and attachments related to handbook, compensation, or policy updates. Attachments are limited to Microsoft Word documents and match similar update-related terminology. This pattern has been observed used to delivery credential phishing via QR codes.
Attachment: Suspicious PDF created with headless browser
Detects PDF documents containing a table of contents that were generated using HeadlessChrome, Chromium with Skia/PDF, or QT with empty metadata fields - common characteristics of automated malicious document creation.
Attachment: Suspicious VBA macro
Detects any VBA macro attachment that scores above a low confidence threshold in the Sublime Macro Classifier.
Attachment: SVG file execution
Detects file execution attempts in SVG files. ActiveXObject is used to invoke WScript.Shell and run a program.
Attachment: SVG file with HTML entity encoded href attributes
Detects SVG file attachments containing href attributes with three or more consecutive HTML numeric entity references, a technique used to obfuscate malicious URLs and evade security scanning.
Attachment: SVG file with hyperlinks and cursor styling
Detects inbound messages containing SVG attachments that include clickable hyperlink elements and CSS pointer cursor styling, which may be used to deceive recipients into clicking malicious links disguised as legitimate images.