Nov 13, 2021
69 Views
0 0

Microsoft warns of surge in HTML smuggling phishing attacks

Written by

AMD fixes dozens of Windows 10 graphics driver security bugs
Void Balaur hackers-for-hire sell stolen mailboxes and private data
Russian ‘King of Fraud’ sentenced to 10 years for Methbot scheme
Windows 10 App Installer abused in BazarLoader malware attacks
This pre-Black Friday deal lets you create a portable triple-screen setup
New Windows 11 build fixes widespread printer issues, system freezes
The Week in Ransomware – November 12th 2021 – Targeting REvil
Microsoft Intune bug forces Samsung devices into non-compliant state
Qualys BrowserCheck
STOPDecrypter
AuroraDecrypter
FilesLockerDecrypter
AdwCleaner
ComboFix
RKill
Junkware Removal Tool
How to remove the PBlock+ adware browser extension
Remove the Toksearches.xyz Search Redirect
Remove the Smashapps.net Search Redirect
Remove the Smashappsearch.com Search Redirect
Remove Security Tool and SecurityTool (Uninstall Guide)
How to remove Antivirus 2009 (Uninstall Instructions)
How to Remove WinFixer / Virtumonde / Msevents / Trojan.vundo
How to remove Google Redirects or the TDSS, TDL3, or Alureon rootkit using TDSSKiller
Locky Ransomware Information, Help Guide, and FAQ
CryptoLocker Ransomware Information Guide and FAQ
CryptorBit and HowDecrypt Information Guide and FAQ
CryptoDefense and How_Decrypt Ransomware Information Guide and FAQ
How to make the Start menu full screen in Windows 10
How to install the Microsoft Visual C++ 2015 Runtime
How to open an elevated PowerShell Admin prompt in Windows 10
How to Translate a Web Page in Google Chrome
How to start Windows in Safe Mode
How to remove a Trojan, Virus, Worm, or other Malware
How to show hidden files in Windows 7
How to see hidden files in Windows
eLearning
IT Certification Courses
Gear + Gadgets
Security
javascript
Microsoft has seen a surge in malware campaigns using HTML smuggling to distribute banking malware and remote access trojans (RAT).
While HTML smuggling is not a new technique, Microsoft is seeing it increasingly used by threat actors to evade detection, including the Nobelium hacking group behind the SolarWinds attacks.
HTML smuggling is a technique used in phishing campaigns that use HTML5 and JavaScript to hide malicious payloads in encoded strings in an HTML attachment or webpage. These strings are then decoded by a browser when a user opens the attachment or clicks a link.
For example, a phishing HTML attachment could include a harmless link to a known website, thus not being seen as malicious. However, when a user clicks on the link, JavaScript will decode an included encrypted or encoded string and convert it into a malicious attachment that is downloaded instead, as shown in the code below.
Since the malicious payload is encoded initially, it looks harmless to security software and is not detected as malicious. Furthermore, as JavaScript assembles the payload on the target system, it bypasses any firewalls and security defenses that would usually catch the malicious file at the perimeter.
Microsoft researchers have seen this technique used in Mekotio campaigns that deliver banking trojans and also in highly-targeted NOBELIUM attacks.
HTML smuggling campaigns are also used to drop the AsyncRAT or NJRAT remote access trojans, or the TrickBot trojan used to breach networks and deploy ransomware.
The attacks usually start with a phishing email containing an HTML link in the body of the message or a malicious HTML file as an attachment.
If either is clicked, a ZIP file is dropped using HTML smuggling. This archive contains a JavaScript file downloader that fetches additional files from a command and control server (C2) to install on the victim’s device.
In some cases, the created archives are password-protected for additional detection evasion against endpoint security controls. However, the password to open it is provided in the original HTML attachment, so the victim must enter it manually.
Once the script is launched, a base64-encoded PowerShell command is executed that downloads and installs the TrickBot trojan or other malware.
A 2020 report from Menlo Security also mentions the Duri malware group as one of the actors who actively uses HTML smuggling for payload distribution, but the technique was first seen in the wild since at least 2018.
Microsoft first warned about a sudden uptick in this activity in July 2021, urging admins to raise their defenses against it.
Microsoft suggests admins use behavior rules to check for commonly characteristics of HTML smuggling, including:
For endpoints, admins should block or audit activity associated with HTML smuggling, including:
In addition to the above, users may prevent automatic JavaScript code execution by associating .js and .jse files with a text editor like Notepad.
Ultimately, the best defense is to train users not to open files downloaded via links in emails and attachments. All files downloaded from an email should be treated with caution and checked carefully before being opened.
Furthermore, if an attachment or email link downloads an attachment ending with a .js extension (JavaScript), it should never be opened and automatically be deleted.
Unfortunately, Windows disables the showing of file extensions by default, leading to extensions not being seen in many cases. This is why it is always suggested that users enable the viewing of file extensions to prevent the opening of malicious files.
Microsoft: Nobelium uses custom malware to backdoor Windows domains
Lazarus hackers target researchers with trojanized IDA Pro
TrickBot teams up with Shatak phishers for Conti ransomware attacks
RAT malware spreading in Korea through webhards and torrents
Political-themed actor using old MS Office flaw to drop multiple RATs
Not a member yet? Register Now
Costco discloses data breach after finding credit card skimmer
Microsoft: New security updates trigger Windows Server auth issues
To receive periodic updates and news from BleepingComputer, please use the form below.
Terms of Use Privacy PolicyEthics Statement
Copyright @ 2003 – 2021 Bleeping Computer® LLC – All Rights Reserved
Not a member yet? Register Now
Read our posting guidelinese to learn what content is prohibited.

source

Article Categories:
Cybersecurity News

Comments are closed.