Brute-force attacks against telnet attempt to gain unauthorized access by systematically trying many combinations of usernames and passwords until the correct one is found.
Risk
If successful, attackers gain remote access to systems, allowing them to steal data, install malware, or use compromised machines in larger attacks. Since telnet transmits data unencrypted, it is especially vulnerable.
Mitigation
Disable telnet where possible and use secure alternatives such as SSH. Enforce strong password policies, use account lockout mechanisms, and deploy intrusion detection tools to block repeated login attempts.
Resources
OWASP Authentication Cheat Sheet
https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html
