best security for remote access ssh

Best Security Practices for SSH (Secure Shell) Remote Access in Cisco.

• 1.Remote access should be via SSH and telnet is disabled.
• 2. SSH should be version 2 or higher. Do not run v1.
• 3. Configure SSH logging.
• 4. Configure Login Banner.
• 5. Configure timestamp, login authentication (exec and session) timeout, ssh only transport input, with ACL configured to allow only authorized IPs ...

Full Answer

How do I Secure my SSH key pairs?

Enhance Linux SSH Security Using Key Pairs One of the most secure methods to authenticate clients to servers is by using SSH key pairs. Strong passwords may be sufficient to keep your server safe, but persistent brute force attacks can still crack them.

How to improve SSH security in Linux?

1. Change the Default SSH Port 2. Enhance Linux SSH Security Using Key Pairs 3. Disable Server SSH Root Login 4. Disable Password-Based Logins on Your Server 5. Restrict SSH Access Using iptables 1. Change the Default SSH Port

How do I restrict SSH access to a Linux server?

Restrict SSH Access Using iptables Minimizing vulnerabilities in your Secure Shell (SSH) protocol is key to ensuring the security of your Linux environment. In this article, we cover the most common Linux SSH security measures you can take to make your servers more secure.

What are SSH backdoor keys and ssh authorized keys?

Backdoor Keys: By default, most SSH implementations (e.g., OpenSSH) allow users to configure their own authorized key files (placing a public key in an account so they can access it using a private key).

Is remote SSH secure?

SSH keys allow you to make connections without a password that are—counterintuitively—more secure than connections that use password authentication. When you make a connection request, the remote computer uses its copy of your public key to create an encrypted message that is sent back to your computer.

How do I protect SSH port 22?

How To Secure SSH ServerAvoid Using Port 22. Port 22 is a default port for SSH connections and every hacker trying to access your SSH server will first attack this port. ... Disable the Root Logins. ... Use SSH Keys Instead of Passwords. ... Disable Empty Passwords.

How do you mitigate SSH vulnerability?

Mitigating SSH based attacks – Top 15 Best SSH Security PracticesSet a custom SSH port.Use TCP Wrappers.Filter the SSH port on your firewall.Disable Root Login.SSH Passwordless Login.Strong passwords/passphrase for ssh users and keys.Set Idle Timeout Interval.Disable Empty Passwords.More items...•

Which one is more secure https or SSH?

While SSH is usually considered more secure, for basic usage of Github, HTTPS authentication with a password is acceptable enough. In fact, Github themselves defaults to and recommends most people use HTTPS.

Is it safe to expose port 22?

As such, Port 22 is subject to countless, unauthorized login attempts by hackers who are attempting to access unsecured servers. A highly effective deterrent is to simply turn off Port 22 and run the service on a seemingly random port above 1024 (and up to 65535).

Is SSH hackable?

Activity reported by web servers has proven attackers are exploiting SSH Keys to gain access to company data. Attackers can breach the perimeter in a number of ways, as they have been doing, but once they get in, they steal SSH Keys to advance the attack.

Does SSH have any vulnerabilities?

The SSH Compensation Attack Detector was introduced to fix this flaw. However, these updated implementations were found to contain a serious integer overflow vulnerability that allowed attackers to execute arbitrary code with the privileges of the SSH daemon, typically root.

Can SSH be brute forced?

SSH is used for remote logins, command execution, file transfer, and more. SSH brute force attacks are often achieved by an attacker trying a common username and password across thousands of servers until they find a match.

How do I block port 22?

Aspera recommends disabling TCP/22 to prevent security breaches of your SSH server. Once your client users have been notified of the port change (from TCP/22 to TCP/33001), you can disable Port 22 in your sshd_config file. To disable TCP/22 and use only TCP/33001, comment-out Port 22 in your sshd_config file.

Is port 22 always open?

By default, port 22 is open on all IBM StoredIQ hosts. The port is used for Secure Shell (SSH) communication and allows remote administration access to the VM.

Is it safe to leave SSH port open?

Keeping the port open and using a strong password leaves the possibility of a brute-force attack guessing the password.

Should SSH be exposed to the Internet?

IMO SSH is one of the safest things to have listen on the open internet. If you're really concerned have it listen on a non-standard high end port.

Why is SSH important?

Because SSH provides remote access into systems, it is critical that access be tracked and controlled. Since many organizations don’t have centralized oversight and control of SSH, the risk of unauthorized access is increasing. Here are a few of these risks:

What are the risks of using SSH private keys?

Here are some of the risks posed to SSH private keys: Careless Users: When users are authorized to use SSH public key authentication, they can be careless in their handling of their private keys, either placing them in insecure locations, copying them to multiple computers, and not protecting them with strong passwords.

Why is SSH pivoting so bad?

And SSHenabled pivoting can be the most damaging because SSH users and automated process are typically granted elevated privileges. Many organizations leave themselves open to SSH-based pivoting because they have no inventory of deployed SSH keys that enable persistent access between systems.

Why are SSH keys so weak?

Weak Keys: Because many SSH keys have not been changed in years, smaller length keys (e.g., 512 or 768-bit keys) are still in use, making it possible for a sophisticated attacker may derive the value of the private key.

How does SSH work?

Dating back to the days where encryption wasn’t available for all protocols, SSH features the ability to forward traffic sent to a local port on an SSH client. The traffic is forwarded through the encrypted SSH session to the SSH server or even beyond. The challenge is that this provides the ability for unapproved communications to traverse firewalls. If the user of an SSH client that has been granted SSH access to a server on the other side of a firewall is allowed to enable local port forwarding, they open the possibility that an attacker can gain access to systems and devices which might otherwise not be accessible. By exploiting port forwarding, an attacker may bypass firewalls that have been setup to limit access to the server’s network. In addition, attackers avoid detection because they are operating over an encrypted SSH connection.

What happens if you allow SSH access to a server on the other side of a firewall?

If the user of an SSH client that has been granted SSH access to a server on the other side of a firewall is allowed to enable local port forwarding, they open the possibility that an attacker can gain access to systems and devices which might otherwise not be accessible.

Why does SSH allow movement?

If not tightly controlled and managed, SSH can enabled that movement (pivoting) between systems because of the persistent trust relationships created with SSH keys.

Where is SSH used?

The SSH protocol is now widely used in data centers and by almost every major enterprise running on any of the UNIX variants. When it comes to security measures, it is essential to combine them, apply them in layers, and not pick just one and rely on only that solution.

What is SSH protocol?

The Secure Shell (SSH) protocol enables cryptographically protected remote system administration and file transfers over insecure networks. Using multiple encryption methods, SSH secures the connection between a client and a server safeguarding the users’ commands, authentication, and output against unauthorized access and attacks.

How to authenticate clients to servers?

One of the most secure methods to authenticate clients to servers is by using SSH key pairs. Strong passwords may be sufficient to keep your server safe, but persistent brute force attacks can still crack them. This is why you need additional SSH hardening with key pairs.

What is a SSH key pair?

An SSH key pair consists of two long series of characters, a private key which is kept secret, and a public key which can be safely shared. Their purpose is similar to passwords, and they allow you to automatically establish an SSH session without the need to type in a password.

Why use a non standard port for SSH?

Using a non-standard port for SSH connection helps avoid automated attacks on your server. It also helps reduce the chances of it appearing on a hacker’s radar and makes it a less obvious target.

Why is it important to keep a private key safe?

This is why it is important to keep the private key safe because it unlocks all the copies of the padlocks you’ve handed out.

Where is the RSA key saved?

The key will be saved in the home user’s directory, in the ~/.ssh directory. To change the location, just type in the new path. The recommendation is to stick with the default location, so you do not have to make any changes to your SSH client. The private, or the identification key, will be saved as id_rsa and the corresponding public key as id_rsa.pub.

What is SSH in Linux?

SSH ( Secure Shel l) is an open-source network protocol that is used to connect local or remote Linux servers to transfer files, make remote backups, remote command execution, and other network-related tasks via scp command or sftp command between two servers that connect on a secure channel over the network.

What is the purpose of the SSH banner?

This is not for any security purpose, but the greatest benefit of this banner is that it is used to display ssh warning messages to UN-authorized access and welcome messages to authorized users before the password prompt and after the user logged in.

What services can be supported by log files?

Support for log files rotation and can handle multiple services like ( sshd, vsftpd, apache, etc).

What is fail2ban?

Fail2ban is one of the most popular open-source intrusion detection / prevention frameworks written in a python programming language. It operates by scanning log files such as /var/log/secure, /var/log/auth.log, /var/log/pwdfail etc. for too many failed login attempts.

What is the first thing that’s required to ensure smooth remote access via a VPN?

The first thing that’s required to ensure smooth remote access via a VPN is to plan out a comprehensive network security policy.

What is remote access VPN?

The most basic form of VPN remote access is through a RAS. This type of VPN connection is also referred to as a Virtual Private Dial-up Network (VPDN) due to its early adoption on dial-up internet.

Why is IPSEC used?

This allows IPSec to protect data transmission in a variety of ways. IPSec is used to connect a remote user to an entire network. This gives the user access to all IP based applications. The VPN gateway is located at the perimeter of the network, and the firewall too is setup right at the gateway.

What is IPSEC encryption?

IPSec is an IP packet authentication and encryption method. It uses cryptographic keys to protect data flows between hosts and security gateways.

Why use two factor authentication for VPN?

Adopting two-factor authentication for remote access through VPN further boosts your network security. Now let’s take a look at why you should choose a particular VPN type as a secure connection methodology instead of the alternatives.

What is the line of defense for remote access?

So, you have a three-layer line of defense working to protect remote access to your network: anti-virus, firewall, and VPN. The network security team should monitor alerts from these defenses constantly.

Should a company use IPSEC VPN?

A company should go for IPSec VPN remote access if it has a strong networking department with the ability to configure each employee’s hardware device individually (installing client software, enforcing security policies etc.).

1. Strong authentication

Hackers are constantly scanning for SSH servers and attempting to brute-force usernames and passwords. It is therefore critical to enforce strong passwords and explicitly disallow remote logins from accounts with empty passwords. Use the open source John the Ripper tool to find any existing weak passwords.

2. Least privilege

Follow the principle of least privilege; it's critical when determining who is allowed to use SSH and how. Limit SSH logins to only those users who need remote access, and ensure those users only have the privileges they need to perform the tasks for which they are responsible.

3. Secure configuration

Patch all SSH servers on a regular basis to ensure they are running the latest software and they employ SSH-2 security. SSH-2 offers better security than SSH-1, which is no longer allowed by several compliance standards.

4. Monitoring and auditing

The above steps are essential before exposing an SSH server to the internet. Once it is live, deploy constant monitoring and auditing. Monitor SSH logins and activity to detect any unusual activity. Conduct regular audits to discover new instances of servers running SSH and to detect any unsanctioned changes to configuration settings.

5. Training

Training is essential. Make users aware of company policies and procedures that cover the use of SSH. Check the authenticity of the public key for an SSH server every time a connection is established to avoid a possible man-in-the-middle attack. SSH keys should never be hardcoded, stored or backed up to source control or public repositories.

6. Key management

Use an SSH risk assessment tool to manage the multitude of SSH keys that may exist within an organization's IT infrastructure. These tools scan a network for SSH servers and then read configuration files to extract the exact location and use of every key. They also test for weaknesses in the configuration.