Hackers are targeting teleworkers with vishing campaign, CISA and FBI warn

Pierluigi Paganini August 22, 2020

The FBI and CISA issued a joint alert to warn teleworkers of an ongoing vishing campaign targeting entities from multiple US sectors.

The Federal Bureau of Investigation (FBI) and the Cybersecurity and Infrastructure Security Agency (CISA) have issued a joint security advisory to warn teleworkers of an ongoing vishing campaign targeting organizations from multiple US industry industries.

Voice phishing is a form of criminal phone fraud, using social engineering over the telephone system to gain access to private personal and financial information for the purpose of financial reward. 

Hackers aim at collecting login credentials for networks of the target organizations, then they attempt to monetize their efforts by selling access to corporate resources in the cybercrime underground.

The campaign is worrisome due to the ongoing COVID-19 pandemic that caused the spike in the number of employees working from home and the increase in the use of corporate VPN 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,” reads the alert.

“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.”

The agencies provide technical details about the attack technique used by cybercriminals.

Threat actors initially registered domains and created phishing pages that look like the company’s internal VPN login page, the hackers also attempt to trick victims into providing two-factor authentication (2FA) or one-time passwords (OTP). Attackers 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

Threat actors compiled dossiers on the employees working for the companies they wanted to target, they gathered their data by scraping of public profiles on social media platforms, recruiter and marketing tools, publicly available background check services, and open-source research.

Attackers collected information such as name, home address, personal cell/phone number, the position at the company, and duration at the company.

Then threat actors directly called employees on their personal cellphones using random Voice-over-IP (VoIP) phone numbers or by spoofing the phone numbers of other company employees.

“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,” continues the alert.

“The actors then convinced the targeted employee that a new VPN link would be sent and required their login, including any 2FA or OTP.”

When the victim provided their data through the phishing site, including 2FA or OTP, the attackers used it in real-time to gain access to the corporate account. In some cases,
bad actors used a SIM-Swap attack on the employees obtain the 2FA and OTP authentication code sent to the victims’ phones.

“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 FBI and CISA said.

The two agencies shared a series of recommendations for companies and their employees:

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.

End-User Tips:

  • Verify web links do not have misspellings or contain the wrong domain.
  • Bookmark the correct corporate VPN URL and do not visit alternative URLs on the sole basis of an inbound phone call.
  • Be suspicious of unsolicited phone calls, visits, or email messages from unknown individuals claiming to be from a legitimate organization. Do not provide personal information or information about your organization, including its structure or networks, unless you are certain of a person’s authority to have the information. If possible, try to verify the caller’s identity directly with the company.
  • If you receive a vishing call, document the phone number of the caller as well as the domain that the actor tried to send you to and relay this information to law enforcement.
  • Limit the amount of personal information you post on social networking sites. The internet is a public resource; only post information you are comfortable with anyone seeing.
  • Evaluate your settings: sites may change their options periodically, so review your security and privacy settings regularly to make sure that your choices are still appropriate.
  • For more information on how to stay safe on social networking sites and avoid social engineering and phishing attacks, visit the CISA Security Tips below:
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Pierluigi Paganini

(SecurityAffairs – hacking, vishing)

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