What are the common vulnerabilities in FTP and how do you avoid them?

I agree, but I don't think it's correct to refer to FTPS or SFTP as "a secure version of FTP" - FTPS is a less insecure version of FTP. SFTP is another less insecure protocol which, despite the similar name, operates in a different way. None of these protocols offer multi-factor authentication. So a much more secure way to transfer files is to use an HTTPS based system which incorporates multi-factor authentication and, ideally, file integrity validation.

Common FTP vulnerabilities include: Brute Force Attacks: Attackers can guess or crack weak FTP passwords. Data Interception: Data transmitted over FTP can be intercepted, exposing sensitive information. Directory Traversal: Attackers may exploit this vulnerability to access unauthorized directories on the server. FTP Bounce Attack: Attackers can use the server as a proxy to attack other servers. Weak Encryption: FTP may use weak encryption or no encryption, making data susceptible to eavesdropping. To avoid these vulnerabilities, use SFTP (SSH File Transfer Protocol) or FTPS (FTP Secure) for encrypted file transfer, employ strong passwords, restrict access, and keep FTP software updated to patch known vulnerabilities.

Weak authentication is the most common vulnerabilities associated with FTP servers. FTP servers typically require users to authenticate themselves before allowing access to the server. However, if the authentication mechanism is weak, it can be easily exploited by attackers. One technique on the rise in the past few years is "credential stuffing". Credential stuffing is when attackers use stolen or leaked usernames and passwords from other sources to gain access to the server. Often they use other credentials meaning passwords and logins that are passed around message boards or bought in bulk from other users on the "dark web".

Weak Passwords are a common vulnerability in FTP. To avoid this issue: Enforce Strong Password Policies: Require complex passwords that include a mix of uppercase and lowercase letters, numbers, and special characters. Regular Password Updates: Implement policies for regular password changes to reduce the risk of password compromise. Multi-Factor Authentication (MFA): Add an extra layer of security by requiring a second form of verification. Limit Login Attempts: Set limits on the number of failed login attempts to prevent brute force attacks. Educate Users: Ensure that users understand the importance of strong passwords and the risks associated with weak ones. By addressing weak passwords, you significantly improve FTP security.

It's true that weak authentication is the most common vulnerabilities associated with FTP servers. FTP servers typically require users to authenticate themselves before allowing access to the server but if the authentication mechanism is weak, it can be easily exploited by attackers.

This is mostly true, but it seems to be a muddled point: 1) FTP doesn't incorporate logging because it's a protocol not a software program. Every FTP server I've ever used does incorporate logging. Though sometimes it must be explicitly turned on. 2) FTP doesn't incorporate granular (item-by-item) access control for a similar reason. Implementations of FTP tend to do so though, either natively or via an underlying operating system. Again the problem is more of poor configurations that fail to do this. 3) Though they're always helpful, it's hard to see how a firewall or VPN are directly relevant to the specific points about granular access and logging. 4) Again, best not to use FTP at all if you care about security. There are better options.

I agree, but to "be careful about the source and the content of the files that you download or execute" the best advice is not to use FTP at all. If wherever you're connecting to refuses to offer a better alternative than FTP, don't use them.

It's misleading to imply this is a specific problem with FTP servers; it's true for any system connected to the internet, which these days is almost everything.