Turning a blind eye: How end-users and NLP AI are being tricked by clever phishing techniques like ZeroFont

Overview

Recently, an older email security detection bypass method was seen being used to successfully surpass Microsoft’s spam and phishing filters. This technique described above makes use of two methods and was dubbed “ZeroFont Phishing” by Avanan. ZeroFont Phishing is the method when attackers insert random strings within keywords or phrases that many artificially intelligent systems use to identify malicious or suspicious content.  When these strings are placed within the HTML span tags mixed with setting the font-size attribute to zero, they become invisible to the end user, but  simultaneously appear to neuter the ability of existing Natural Language Processing (NLP), Machine Learning (ML), and Artificial Intelligence (AI) systems to understand what is in the plaintext of the email. In the majority of implementations NLP attempts to understand the meaning of email text to determine context and patterns that will assist in overall classification. These methods are not new, so we decided to take a deeper look at these older techniques and explore the potential variants that could have similar results.

More Windows Software Abuse: Microsoft Excel Query Files Used to Deliver Malware

Cofense Intelligence™ recently analyzed a phishing campaign that distributed Microsoft Excel Query files in an infection chain to deliver the AmmyyAdmin remote access trojan (RAT). But analysts noted that this latest campaign bore a striking resemblance to another campaign in March 2018 in which phishing emails were used to distribute .URL internet shortcut files.

Russian “Troldesh” AKA Encoder.858 or Shade is back!

Posted by: Dilen Thakuri, Cofense Phishing Defense Center

On the 19th of April, the Cofense Phishing Defense Center received an email crafted to appear to be from “Sberbank Russia.” In fact, it was a phishing email containing the Troldesh malware, a variant of Russian Ransomware first seen in mid-2015. The PDC hadn’t seen this variant for quite some time.

Their email filters missed these threats. Good thing the users didn’t.

By Jerome Doaty, Zakari Grater, and Brenda Gooshaw Samson

Technology is an important part of any phishing defense, especially perimeter tech designed to filter emails. But these systems, even those billed as “next-gen email security platforms,” don’t catch everything. Some phishes always get through.

Examples of Silver-bullet Technology Fails

Most security teams today are pretty much in the same boat: limited budget, limited man power, and limited time to defend their network against escalating threats and attacks.  Perhaps that’s why so many information security vendors claim to have the “silver bullet” to protect the customer’s environment and solve their problems. 

Phishing attack shut down in 19 minutes with Cofense Triage.

Imagine a cunning phisher: he knows his craft and sends your users an email appearing to come from your CEO that bypasses all your other technology. What would you do?

One of our customers faced that very scenario and relied on Cofense TriageTM and the Cofense Phishing Defense Center (PDC) to analyze and respond to the attack in less than 20 minutes after it launched.

Analysing TrickBot Doesn’t Have to be Tricky

New additions to the TrickBot malware’s capabilities, observed by the Phishing Defence Centre, indicate that this malware tool is undergoing active development. The designers of this malware are still working hard to introduce new functionality including a network worm functionality and a screen-lock module. The worm component utilises the leaked “EternalBlue” exploit for CVE-2017-0144 to propagate itself across networks that have yet to patch or discontinue the use of SMBv1. The deployment of the screen-lock module (which appears to be still in the early phases of development) gives the threat actors the ability to change the functionality of the malware from robust banking trojan to a rudimentary ransomware.