Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Threat Intelligence

JavaScript Obfuscation Moves to Phishing Emails

Attackers are hiding malicious payloads in phishing emails via a technique traditionally used to hide malicious code planted on websites.

JavaScript, the ubiquitous scripting language used across Web applications worldwide, is becoming a key ingredient in phishing campaigns looking to plant malicious code on victims' computers, new research shows.

Phishing attacks using JavaScript obfuscation techniques rose more than 70% from November 2019 through August 2020, according to Akamai lead researcher Or Katz.

Katz says that the reason for the rise in this attack technique is simple. "The fact that JavaScript is a scripting language that runs on the client side gives [attackers] the ability to create content, but only once that content is rendered on the browser of the potential victims, will the actual page be rendered and be presented to the victim," Katz says. "Only at that point in time will you see the actual phishing website asking for credentials or other personal information."

In the first of a series of blog posts on his research, he said "content escaping," while not a sophisticated obfuscation technique, is effective at hiding - or obfuscating - the malicious content of a message. It is also far more commonly used on malicious websites than in phishing or scam email messages. It's the technique's growing use in email that caught Katz's attention.

JavaScript has been used in fairly simple obfuscation techniques, but the obfuscation is becoming more sophisticated, he found. Take XOR decryption, which he's seeing in more and more campaigns. XOR (exclusive-or) is a technique taken from cryptography that makes contents smaller while creating a block of text that is unique for each message. The result is something that can't easily be defeated by simple signature-matching anti-malware techniques.

Katz then took a closer look a specific campaigns using the JavaScript obfuscation techniques. He notes In the second blog post that single malicious email messages are now carrying JavaScript code that uses multiple obfuscation and re-direction techniques, including URL cloaking, content escaping, and polymorphic functions at the same time. These techniques are "just the tip of the iceberg, as more complex techniques, including huge chunks of embedded dead code and anti-debugging, are constantly being used in the wild," he said in the post.

Related Content:

99% of Websites at Risk of Attack Via JavaScript Plug-ins

2020 State of Cybersecurity Operations and Incident Response

New on The Edge: Why Defense, Not Offense, Will Determine Global Cyber Powers

He told Dark Reading he believes JavaScript obfuscation will increase in email phishing attacks.

"There is a movement from using solely emails as a way to propagate phishing scams into social networks and messaging and social messaging platforms to deliver a lot of those scams," he says. "When you try to distribute attacks through of social media, then you are actually using the power of that platform to do a very rapid kind of distribution that is dependent on the trustworthiness of the people that are distributing them."

Because the techniques are being so successful, Katz says that they're not limited to a single criminal organization or geographic area: they're being used worldwide by a wide variety of threat actors. And because they can come from so many sources, and hide in so many ways, Katz says that basic user education may still be one of the most powerful tools to use against them.

It starts, he says, with reminding users that an email message that seems too good to be true probably is. And if the URL seems unusual, or appears from an unusual location in a message or on a Web page, that should be a red flag.

"Stop at that point, think twice and try to figure out if you need to give any personal information." If it's suspicious enough to make you think, he says, then it's almost certainly suspicious enough to make you stop.

Curtis Franklin Jr. is Senior Editor at Dark Reading. In this role he focuses on product and technology coverage for the publication. In addition he works on audio and video programming for Dark Reading and contributes to activities at Interop ITX, Black Hat, INsecurity, and ... View Full Bio
 

Recommended Reading:

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
vtompkins105
50%
50%
vtompkins105,
User Rank: Apprentice
10/30/2020 | 12:46:55 PM
Can't always expect the wetware to do the right thing.
I know too many people who don't question anything they read in an email or on social media. To now expect them to anylize it - it won't happen.Just look at all the users who like, share, or copy/paste on Facebook and which indicates they need to be protected from themselves.

WARNING: Don't try this at home!

I myself tend to disable ALL firewals and run a script blocker in my browser. When I do run virus scans - via USB bootable - they only find cookies or the PUPs I put there. I even disable Windows Defender because it keeps deleting my PUPs without giving me an option.
Edge-DRsplash-10-edge-articles
7 Old IT Things Every New InfoSec Pro Should Know
Joan Goodchild, Staff Editor,  4/20/2021
News
Cloud-Native Businesses Struggle With Security
Robert Lemos, Contributing Writer,  5/6/2021
Commentary
Defending Against Web Scraping Attacks
Rob Simon, Principal Security Consultant at TrustedSec,  5/7/2021
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win an Amazon Gift Card! Click Here
Latest Comment: What Virtual Reality phishing attacks will look like in 2030.
Current Issue
2021 Top Enterprise IT Trends
We've identified the key trends that are poised to impact the IT landscape in 2021. Find out why they're important and how they will affect you today!
Flash Poll
How Enterprises are Developing Secure Applications
How Enterprises are Developing Secure Applications
Recent breaches of third-party apps are driving many organizations to think harder about the security of their off-the-shelf software as they continue to move left in secure software development practices.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2021-21652
PUBLISHED: 2021-05-11
A cross-site request forgery (CSRF) vulnerability in Jenkins Xray - Test Management for Jira Plugin 2.4.0 and earlier allows attackers to connect to an attacker-specified URL using attacker-specified credentials IDs obtained through another method, capturing credentials stored in Jenkins.
CVE-2021-21653
PUBLISHED: 2021-05-11
Jenkins Xray - Test Management for Jira Plugin 2.4.0 and earlier does not perform a permission check in an HTTP endpoint, allowing with Overall/Read permission to enumerate credentials IDs of credentials stored in Jenkins.
CVE-2021-21654
PUBLISHED: 2021-05-11
Jenkins P4 Plugin 1.11.4 and earlier does not perform permission checks in multiple HTTP endpoints, allowing attackers with Overall/Read permission to connect to an attacker-specified Perforce server using attacker-specified username and password.
CVE-2021-21655
PUBLISHED: 2021-05-11
A cross-site request forgery (CSRF) vulnerability in Jenkins P4 Plugin 1.11.4 and earlier allows attackers to connect to an attacker-specified Perforce server using attacker-specified username and password.
CVE-2021-21656
PUBLISHED: 2021-05-11
Jenkins Xcode integration Plugin 2.0.14 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.