Compromised Account Used to Launch Internal Phishing Attack

August 9, 2020

Compromised accounts are commonly used by cybercriminals to send additional attacks because they appear to originate from a trustworthy source—typically a known partner or customer, or a known coworker within the organization. In this attack, the account was first compromised, and then attackers used it to launch internal phishing attacks to gain access to additional accounts.

Summary of Attack Target

  • Platform: Office 365
  • Email Security: Proofpoint
  • Victims: Internal Employees
  • Payload: Malicious Link
  • Technique: Compromised Internal Account

Overview of the Internal Phishing Atack

In this attack, the email itself is simple and masquerades as an encrypted message notification related to a OneDrive for Business file. It appears to come from an internal account and is sent to a known coworker, asking them to open the message.

If the recipient clicks on the link, it takes them to a PDF hosted on a Russian domain, which guides victims to click on another link to view and download the supposed file. After clicking the second link, the victims are taken to a phishing page.

The phishing page asks the victim to enter their Microsoft credentials in order to access the document. Should victims fall for this attack, they risk further compromise within their company as the attacker gains access to more OneDrive and Microsoft Office accounts, from which they can steal valuable and sensitive information, hijack existing conversations, or create new attacks on other employees.

Why Compromised Accounts are Effective for Phishing

By utilizing a compromised internal account, the attacker is able to bypass any external email filtering set in place by the company, as most traditional infrastructure does not view internal-to-internal, or east-west traffic. In addition, it is easier to deceive recipients of this email, as the email appears to be coming from a coworker.

In addition, the link in the email is hidden in the text of the company’s name, and the link hosted on the Russian domain is concealed in the text that says “VIEW ONLINE / DOWNLOAD”. After clicking the links, victims are taken to a phishing page tailored specifically to their company.

Abnormal stopped this attack due to a variety of malicious signals. Most notably, the attacker sent the original email from an IP located in the United Kingdom, which is suspicious because this sender never sends from the UK, and the recipient rarely receives emails from there either. Combined with the BCC recipient pattern and the suspicious link, it's clear that this account has been compromised and is now being used to attack the organization.

To learn how Abnormal can detect account takeovers within your organization, request a demo today.

Related Posts

B 12 03 22 SIEM
Learn about Abnormal’s enhanced SIEM export schema, which provides centralized visibility into email threats
Read More
Blog phishing cover
The phishing email is one of the oldest and most successful types of cyberattacks. Attackers have long used phishing as a common attack vector to steal sensitive information or credentials from their victims. While most phishing emails are relatively simple to spot, the number of successful attacks has grown in recent years.
Read More
Blog brand cover
For those of you who have visited the Abnormal website over the last month, you’ve seen something different—a redesigned brand focused on precision. It’s new and innovative, and different from any other cybersecurity company, because it was created with one thing in mind: our customers.
Read More
B 11 22 21 AAA
At Abnormal, our customers have always been our biggest priority. Customer obsession is one of our five company values, and we live this every single day as we provide the best email security protection available for the hundreds of companies who entrust us to protect their mailboxes.
Read More
Blog microsoft abnormal cover
Before we jump into modern threats, I think it’s important to set the stage ​​since email has been around. Since email existed, threat actors targeted email users with malicious messages, general spam, and different ways to take advantage of the platform. Then of course, more dangerous attacks started to come up… things like malware and other viruses.
Read More
Blog black friday scam cover
While cybersecurity awareness is a year-round venture, it is especially important to be mindful during certain times of the year. With Thanksgiving here in the United States on Thursday, our thoughts will likely be on our family and friends and everything we have to be thankful for this holiday season.
Read More
Blog automation workflows cover
Our newest platform capabilities help customers streamline critical security workflows, like triaging phishing mailbox submissions or triggering tickets to investigate account takeovers, through automated playbooks. Doing so can decrease mean time to respond (MTTR) to incidents, further reducing any potential risk to the organization and eliminating manual workflows to save time and increase the efficiency of IT and security teams.
Read More
Blog tsa scam cover
On November 9, 2021, we identified an unusual phishing email that claimed to be from “Immigration Visa and Travel,” inviting the recipient to renew their membership in the TSA PreCheck program. The email wasn’t sent from a .gov domain, but the average consumer might not immediately reject it as a scam, particularly because it had the term “immigrationvisaforms” in the domain. The email instructed the user to renew their membership at another quasi-legitimate-looking website.
Read More
Blog pyspark cover
At Abnormal Security, we use a data science-based approach to keep our customers safe from the most advanced email attacks. This requires processing huge amounts of data to train machine learning models, build datasets, and otherwise model the typical behavior of the organizations we’re protecting.
Read More
Blog tiktok attack cover
As major social media platforms have expanded the ability of creators to monetize their content in the last few years, they and their users have increasingly found themselves the targets of malicious activity. TikTok is now no exception.
Read More
Blog ransomware guide cover
While various state agencies and the private sector keep track of ransomware attacks and related tactics worldwide, malicious actors change and evolve their ransomware strategies all the time. We’ve put together a comprehensive guide that will define ransomware, how to detect it, and what steps to take if you’ve fallen victim to a ransomware virus attack.
Read More
Blog detection efficacy cover
One of the key objectives of the Abnormal platform is to provide the highest precision detection to block all never-before-seen attacks. This ranges from socially-engineered attacks to account takeovers to everyday spam, and the platform does it without customers needing to create countless rules like with traditional secure email gateways.
Read More