TCP Remote Access

Port 2222 (SSH Alternate)

Learn about port 2222 (SSH Alternate) - security risks, vulnerabilities, and common uses. Find devices with port 2222 open.

Quick Info

Port Number

2222

Protocol

TCP

Service

SSH Alternate

IANA Name

SSH Alternate

Service Description

TCP port 2222 is commonly used as an alternative port for the Secure Shell (SSH) protocol. SSH, by default operating on port 22, provides a secure, encrypted channel for remote administration, file transfer (using SFTP or SCP), and port forwarding. Using a non-standard port like 2222 is a form of security through obscurity, aiming to reduce automated attacks that target the default SSH port. The rationale behind using an alternate port is that automated bots and scripts scanning for open SSH servers often only target port 22, making servers listening on other ports less likely to be detected during broad network scans. However, it's crucial to understand that this provides only a minor security benefit; a determined attacker can still find the open port through port scanning.

Technically, when an SSH server is configured to listen on port 2222, the server process binds to this port and listens for incoming TCP connections. When a client initiates a connection to the server on port 2222, the server performs a handshake to establish an encrypted connection. This handshake involves key exchange algorithms (like Diffie-Hellman or Elliptic-curve Diffie-Hellman) and symmetric encryption algorithms (like AES or ChaCha20) to protect the confidentiality and integrity of the data transmitted between the client and the server. The SSH protocol itself remains the same, regardless of the port used.

## Firewall Recommendations

Whether to allow or block port 2222 depends on whether you are running an SSH server on this port. If you are not, it should be blocked. If you are running an SSH server on port 2222, the following best practices should be followed: 1) Implement strong passwords or, preferably, public key authentication. 2) Enable multi-factor authentication (MFA). 3) Use a firewall to restrict access to port 2222 to only trusted IP addresses or networks. 4) Keep the SSH server software up to date to patch security vulnerabilities. 5) Consider using intrusion detection/prevention systems (IDS/IPS) to monitor for suspicious activity on port 2222. 6) Disable root login over SSH. 7) Implement rate limiting to prevent brute-force attacks. 8) Regularly review SSH server logs for suspicious activity.

Security Information

Using port 2222 for SSH, while offering a slight reduction in automated scans, does not eliminate security risks. Attackers can still perform port scans to identify open ports, including 2222. Brute-force attacks, dictionary attacks, and credential stuffing attacks remain viable threats. Vulnerabilities in the SSH server software itself can be exploited regardless of the port used. Furthermore, misconfiguration of the SSH server, weak passwords, and lack of multi-factor authentication can render the server vulnerable. Attackers often target SSH servers to gain unauthorized access to systems, install malware, or use the compromised system as a jumping-off point for further attacks within the network. The perceived obscurity of using a non-standard port can lead to a false sense of security, potentially resulting in lax security practices.

Known Vulnerabilities

CVE	Name	Severity	Description
CVE-2023-51385	OpenSSH Authentication Bypass Vulnerability	Critical	An authentication bypass vulnerability exists in OpenSSH versions before 9.6, allowing attackers to potentially gain unauthorized access to accounts without proper authentication. Although not specific to port 2222, the vulnerability is applicable if OpenSSH is running on this port.
CVE-2020-14145	libssh Authentication Bypass Vulnerability	High	A flaw in libssh's server-side state machine allows authentication bypass in certain configurations. If a server using libssh listens on port 2222, it could be vulnerable.
CVE-2018-15473	OpenSSH User Enumeration Vulnerability	Medium	OpenSSH versions before 7.7 have a user enumeration vulnerability. While not specific to port 2222, it can be exploited if OpenSSH runs on that port, allowing attackers to determine valid usernames.
CVE-2016-0777	OpenSSH Roaming Feature Vulnerability	Medium	OpenSSH before 7.2 contains a vulnerability related to the roaming feature, potentially leading to information disclosure. While not port-specific, this can affect servers running on port 2222.