We have recently identified some targeted social engineering/phishing attacks of elevated sophistication attempting to engineer fraudulent wire transfers. In these situations, the attacker has displayed knowledge of who inside the organization might be capable of authorizing a transfer. They will then spoof an email chain that shows a fake history with the appropriate people necessary for sign off having already authorized the funds transfer, and the email comes from a sender that differs only by a single character from a legitimate request, making it very difficult to spot visually.
This type of attack relies upon tricking people with email content and contains no technical exploits, so our sensor cannot offer any direct protections against this type of threat.
We can, however, make recommendations you can use to improve the security of internal processes for authorizing funds transfers (or any other sensitive activity) so that the process is not vulnerable to these types of attacks. Since a spoofing attack relies upon the recipient who is making the transfer being unable to reliably verify the authenticity of the sender, the best defense against this is to incorporate something that reliably authenticates each user on the chain and confirms the message content was sent by a specific person.
Though the attacks we have seen to date specifically attempt to engineer wire transfers, the defence steps we outline below can help to safeguard you in any situation where an attacker might want to gain access to confidential information or trick an employee into doing some unauthorized action through social engineering via email.
• Make sensitive actions require two-factor authorization, such as a phone call using a pre-shared number
(from outside the email) to verify the email's authenticity.
• Provide training to employees that attackers will use these types of spoofing attacks which might only differ
by a single character to raise awareness of the threat.
In terms of email, there are also a number of asymmetric encryption options available to provide digital signatures for email that can be authenticated by the recipient. If email is required to be trusted, we would recommend implementing one of these solutions into the mail client of anyone who has the authority to initiate a sensitive action as well as the clients of those who can initiate the action, and requiring every message authorizing a sensitive action to be digitally signed. Thus, anyone on the chain would have cryptographic evidence that they can trust the email history as being genuine whenever a request comes in through normal channels.
eSentire does not have any particular cryptographic solution that we endorse, however here are some commonly used options we know of for implementing digitally signed email:
• Symantec's PGP solution (full support contracts available for desktop & mobile clients)
• GnuPG (more difficult to implement as there is less support, but fully open source & free)
These solutions will typically require some training on how to use them effectively that will need to be provided to everyone who is using them to verify authenticity, but once set up allow for faster verification.
