Final answer:
Attackers with valid credentials and RADIUS traffic access can perform cryptanalytic attacks to discover the RADIUS shared secret, leading to MitM attacks or packet forgery. Protecting the shared secret and network monitoring is crucial.
Step-by-step explanation:
If attackers have valid credentials including a known password and are able to monitor RADIUS traffic, there are several types of attacks they can execute against a RADIUS shared secret. RADIUS relies on a shared secret for encryption, so if an attacker can capture enough RADIUS traffic, they can perform a cryptanalytic attack. After capturing a substantial amount of data, an attacker may attempt to recover the shared secret through methods such as brute force attacks, dictionary attacks, or more sophisticated cryptographic attacks, since the shared secret is used to encrypt the passwords and other sensitive information within RADIUS responses.
Once the shared secret is compromised, attackers may perform a man-in-the-middle (MitM) attack, where they can alter or inject RADIUS messages between the client and server. They could potentially authorize unauthorized access, modify user privileges, or intercept sensitive information. Another concern is the ability to forge RADIUS packets, potentially giving the attacker the ability to masquerade as a legitimate user or even create administrative users on the system.
It is critical for organizations to protect their RADIUS shared secrets and continually monitor for any unusual activity on their networks, as well as implement robust encryption mechanisms to protect against such attacks.