An ongoing phishing campaign delivering fake Office 365 password expiration reports has managed to compromise tens of C-Suite email accounts to date, according to a warning from anti-malware vendor Trend Micro.
Targeting organizations in finance, government, manufacturing, real estate, and technology sectors, the campaign has claimed victims in Japan, the United States, U.K., Canada, Australia, and several European countries.
To date, more than 300 unique compromised URLs were identified, along with 70 e-mail addresses from eight websites. The phishers were able to compromise 40 legitimate email addresses of CEOs, directors, company founders, and owners, as well as those of other enterprise employees.
As lures, the attackers used fake Office 365 password expiration reports, requesting the victim to click on an embedded link that would allegedly allow them to continue using the same password. However, once the potential victim clicks on the “Keep Password” option, they are taken to the phishing page.
Compromised infrastructure and stolen credentials are abused to host phishing pages and target more victims.
As part of the attack, the hackers used a phishing kit that was first detailed last year, when used in similar attacks leveraging fake Microsoft login pages. Available for purchase, the kit allows cybercriminals to validate stolen credentials.
Trend Micro also discovered that cybercriminals are advertising stolen credentials for Office 365 accounts of CEOs, chief financial officers (CFOs), and employees in the finance department, among others.
“Those posts were seen in multiple English- and Russian-speaking forums, including an underground forum that seemingly matched with another user’s advertisement. Notably, all posts on the Russian-speaking forums were done in English and using recently registered accounts,” Trend Micro explains in a blog post.
Most of the phishing emails in this campaign were sent using a virtual private server (VPS) from FireVPS, a firm that provides customers with various Windows remote desktop protocol (RDP) plans.
Trend Micro says they alerted the company of its service being abused in the phishing campaign, but hasn’t heard back yet.
The phishing kit, which appears to be the evolution of similar toolkits, also includes an extensive list of IP address ranges and domain names, aiming to block access for security companies and large cloud providers, likely in an attempt to evade detection.
The phishing kit’s developer is actively advertising the creation on social media sites and is engaged in the selling of stolen credentials. Trend Micro was eventually able to link the developer’s business Facebook page with the personal one, and has already provided authorities with details on the issue.
Trend Micro also linked sites abused in this campaign to other phishing attacks, including one that exclusively targeted company CEOs, presidents, and founders in the United States. Another campaign targeted directors and managers from Canada, Israel, Hungary, the Netherlands, the UK, and the US.
The email addresses of CEOs in the United States are clearly the main target of this campaign and others using the same phishing kit. Such emails allow attackers to conduct further phishing, compromise sensitive information, and conduct business email compromise (BEC) and other social engineering attacks.
“Phishing attacks and attackers often target employees — usually the weakest link in an organization’s security chain. […] By selectively targeting C-level employees, the attacker significantly increases the value of obtained credentials as they could lead to further access to sensitive personal and organizational information, and used in other attacks,” Trend Micro concludes.