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Cyber Criminals Eye Increased Telework Through Vishing Campaign

August 21, 2020

The Federal Bureau of Investigation (FBI) and Cybersecurity and Infrastructure Security Agency (CISA) issued an advisory in response to a voice phishing campaign.

The COVID-19 pandemic has resulted in a mass shift to working from home, resulting in increased use of corporate virtual private networks (VPNs) and elimination of in-person verification. In mid-July 2020, cybercriminals started a vishing campaign—gaining access to employee tools at multiple companies with indiscriminate targeting—with the end goal of monetizing the access. Using vished credentials, cybercriminals mined the victim company databases for their customers’ personal information to leverage in other attacks. The monetizing method varied depending on the company but was highly aggressive with a tight timeline between the initial breach and the disruptive cashout scheme.

TECHNICAL DETAILS

The initial steps of this vishing campaign followed a common thread. Actors registered domains and created phishing pages duplicating a company's internal VPN login page, also capturing two-factor authentication (2FA) or one-time passwords (OTP). Actors also obtained Secure Sockets Layer (SSL) certificates for the domains they registered and used a variety of domain naming schemes, including the following examples:

• support-[company]

• ticket-[company]

• employee-[company]

• [company]-support

• [company]-okta

Actors then compiled dossiers on the employees at the specific companies using mass scraping of public profiles on social media platforms, recruiter and marketing tools, publicly available background check services, and open-source research. Information collected included: name, home address, personal cell/phone number, position at company, and duration at company.

Actors first began using unattributed Voice over Internet Protocol (VoIP) numbers to call targeted employees on their personal cellphones, and later began incorporating spoofed numbers of other offices and employees in the victim company. The actors used social engineering techniques and, in some cases, posed as members of the victim company’s IT help desk, using their knowledge of the employee's personally identifiable information—including name, position, duration at company, and home address—to gain the trust of the targeted employee. The actors then convinced the targeted employee that a new VPN link would be sent and required their login, including any 2FA or OTP.

The actor logged the information provided by the employee and used it in real-time to gain access to corporate tools using the employee’s account.

In some cases, unsuspecting employees approved the 2FA or OTP prompt, either accidentally or believing it was the result of the earlier access granted to the help desk impersonator. In other cases, attackers have used a SIM-Swap attack2 on the employees to bypass 2FA and OTP authentication.

The actors then used the employee access to conduct further research on victims, and/or to fraudulently obtain funds using varying methods dependent on the platform being accessed.

The COVID-19 pandemic has resulted in a mass shift to working from home, resulting in increased use of corporate VPN and elimination of in-person verification, which can partially explain the success of this campaign. Prior to the pandemic, similar campaigns exclusively targeted telecommunications providers and internet service providers with these attacks but the focus has recently broadened to more indiscriminate targeting.

MITIGATIONS

Organizational Tips

• Restrict VPN connections to managed devices only, using mechanisms like hardware checks or installed certificates, so user input alone is not enough to access the corporate VPN.

• Restrict VPN access hours, where applicable, to mitigate access outside of allowed times.

• Employ domain monitoring to track the creation of, or changes to, corporate, brand-name domains.

• Actively scan and monitor web applications for unauthorized access, modification, and anomalous activities.

• Employ the principle of least privilege and implement software restriction policies or other controls; monitor authorized user accesses and usage.

• Consider using a formalized authentication process for employee-to-employee communications made over the public telephone network where a second factor is used to authenticate the phone call before sensitive information can be discussed.

• Improve 2FA and OTP messaging to reduce confusion about employee authentication
attempts.

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