By: Kian Mahdavi, Cofense Phishing Defense Center
With the escalation of COVID-19, organizations are rapidly adjusting as they move their workforce to work from home; it’s no surprise that threat actors have followed suit. Over the past few weeks, the Cofense Phishing Defense Center (PDC) has observed a notable uptick in phishing campaigns that exploit the widely used Microsoft Sway application to steal organizational credentials and to host phishing websites. Sway is a free application from Microsoft that allows employees to generate documents such as newsletters and presentations and is commonly used by professionals to conduct their regular day to day work tasks.
In a new campaign, threat actors send emails with subject lines such as ‘Employee Enrollment Required’ and ‘Remote Work Access.’
Figure 1: Email body
The sender in Figure 1 claims to come from ‘Human Resources.’ Closer inspection, however, reveals the actual sender’s address – a purchased domain address ‘chuckanderson.com’ with no association to the HR team or the organization’s official mailing address. The attack includes carefully thought out trigger words, such as ‘expected’ and ‘selection/approval,’ language that often trips up employees who are accustomed to receiving occasional emails from their local HR team, especially during this pandemic. Should users hover over the link within the email, however, they would see ‘mimecast.com’ along with ‘office.com,’ potentially and mistakenly deeming these URL(s) as non-suspicious.
By using trusted sources such as Sway to deliver malware or steal corporate credentials, such campaigns often evade Secure Email Gateways (SEGs) thanks to the trusted domains, SSL certificates and URL(s) used within the email headers.
Figure 2: Cofense PDC Triage flagging the known malicious URL
Numerous employees across a variety of departments within the same company received and reported this email to the Cofense PDC, with each email consistently redirecting users to similar Sway URLs. These URLs were already known by our Cofense Triage solution and were identified as malicious, providing valuable context for our PDC analysts when they commenced their investigation.
As previously discussed, as legitimate domains and URLs were used, these campaigns remained undetected for longer periods of time, likely leading to a higher number of compromised account credentials. On the other hand, malicious content hosted on purpose-built phishing sites usually gets flagged much quicker, taken down earlier, and therefore leading to a much shorter ‘time to live’ period. In short, this attack was easy to execute, required minimal skill, and remained undetected by security technologies.
Figure 3: Virus Total URL Analysis
Upon conducting a web search using reliable threat intelligence feeds, as shown above in Figure 3, the authenticity of URLs can be verified against trusted security vendors that have recently detected the attack, flagging them as ‘malicious/phishing’. Displayed in the top right-hand side of Figure 3 is the timestamp revealing the latest known update from a security vendor.
Figure 4: First phase of phishing page
Awaiting the user is the bait on a generic looking page, a ‘BEGIN ENROLLMENT’ button and once clicked, redirects to a document hosted on SharePoint as seen below in Figure 5.
Figure 5: Second phase of phishing page
Once employees enter their credentials and hit the ‘Submit’ button, their log-in information is sent to the threat actor – the end user is none the wiser that they have been successfully phished.
As employees have rapidly shifted to remote working, threat actors have started to look at ways they capitalize on the COVID-19 pandemic to spoof new corporate policies and legitimate collaboration tools to harvest valuable corporate credentials, a trend we anticipate will only continue to gain steam in the foreseeable future.
Indicators of Compromise:
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How Cofense Can Help
Visit Cofense’s Remote Work Phishing Infocenter to stay up to date as threats evolve. Our site is updated with screenshots as we continue to track campaigns.