Phishers are constantly coming up with new ways to evade security solutions, steal credentials, and distribute malware. In January, two new tactics were observed in separate phishing campaigns, one hides malicious URLs from security solutions in a credential-stealing campaign, and the other uses OneNote attachments for distributing malware.
Blank Image Phishing Attacks
The blank image phishing attack involves hiding a Scalable Vector Graphics (SVG) image file within an HTML document sent via email. In this campaign, the email claims to include a DocuSign document, which office workers are likely to be familiar with. The email claims the document includes remittance advice. The user is required to click to view the document and will be directed to the legitimate DocuSign webpage if they do.
However, the attack starts when the user clicks to view the HTML document. The document contains a Base64 blank image file, which has embedded JavaScript that will redirect the victim to a malicious URL. The image itself contains no graphics, so does not render anything on the screen. It is just used as a placeholder for the malicious script. The URL that the user is directed to will prompt them to enter sensitive information. A similar technique using SVG files has previously been used to distribute QBot malware. Many email security solutions ignore HTML files, which increases the chance of the malicious email landing in inboxes. Security teams should consider blocking or quarantining HTML emails to protect against these types of attacks.
OneNote Attachments Used to Distribute Malware
Another campaign has been detected that uses OneNote attachments in phishing emails for distributing remote access malware, which can provide initial access to a victim’s system allowing further malicious payloads to be delivered, such as information stealers and ransomware. For many years, Office documents were the preferred attachment for distributing malware. These files can include macros that download a malicious payload, but Microsoft now blocks macros by default in Office files delivered via the internet, which has forced hackers to look for new ways to distribute their malware.
One new tactic is the use of OneNote attachments. OneNote is installed by default with Microsoft Office and Microsoft 365, which means OneNote files can be opened on most devices even if the user does not use the OneNote application. The lures used in these emails vary, although some of the intercepted emails claimed to be shipping notifications, with the details of the shipment included in the OneNote file.
OneNote files cannot contain macros, but it is possible to insert VBS attachments into a NoteBook. When opening the file, the user is told they must double-click to view the file. Doing so will launch the VBS script, which will download and install malware from a remote site. If the user does click, they will be warned that opening attachments can harm their computer. If that warning is ignored and the user chooses to open the attachment, the script will download a decoy OneNote file – a genuine file – so the user is unlikely to realize that anything untoward has happened, but the script will execute a batch file in the background and will install the second downloaded file, which is malware.
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How to Defend Against Phishing Attacks
Cybercriminals are constantly developing new methods for distributing malware and stealing credentials, and phishing is the most common way to do this. Defending against these attacks requires a defense-in-depth approach, involving multiple overlapping layers of protection. If anyone measure fails to detect a threat, others are in place to detect and block the threat.
In addition to a secure email gateway or spam filter, businesses should consider a web filter for blocking the web-based component of the attack, multifactor authentication for all accounts, antivirus software/endpoint security solutions, and security awareness training for employees to help them identify and avoid phishing threats. For assistance improving your defenses against phishing, contact TitanHQ.