Protection against unauthorized remote logins to your cloud server is a matter of SSH key-based authentication, a strict security policy on the firewall, two-factor authentication, and a secure communication channel – no individual component will give adequate protection by itself. The major risk point in breaches is not the server but the open door to remote login. To patch that vulnerability, you need a series of countermeasures, not a magical setting.
Why Remote Server Access Is a Common Attack Vector
Every cloud server exposes at least one remote access point – usually SSH on port 22 – and that port is scanned constantly by bots looking for weak credentials. Password-based login is the most common way a system can be attacked by brute force, and it is quite common with a standard setup that the system is left in a state where an admin/user of that system – “root user” – can log in directly by guessing the user ID and the password combination. Add in shared team credentials, forgotten firewall rules from old projects, and staging servers left publicly reachable, and it’s clear why misconfigured remote access – not zero-day exploits – is behind most cloud server compromises. The fix is simple, though you’ll need to do some setup yourself instead of trusting the default setting.
How to lock down SSH access in the right way
The best way to secure remote access is through a series of small improvements rather than one major overhaul. The following is a real working method:
- Switch to SSH key authentication, then turn off password login completely in the same location: sshd_config. Keys are far harder to brute-force than passwords.
- Disable root login over SSH and require a non-root user with sudo privileges instead; this is a security advantage that even without any change, one key compromising would limit the impact.
- Change the default SSH port away from 22 to cut down on automated scanning noise (not a security measure on its own, but it reduces log clutter).
- Restrict access by IP using your firewall or security group, allowing SSH only from known office or VPN IP ranges rather than the entire internet.
- Add a VPN as a connection layer for anyone accessing servers from outside a trusted network – a VPN like Planet VPN’s free VPN service can encrypt the connection between a remote worker’s laptop and the server before SSH traffic ever leaves their device, which matters especially on public wi-fi or shared networks.
Every step you take closes the doors that the attacker may open slightly, and when you combine everything, you would have a door to a series of locked gates.
Why Do I Need a Bastion Host?
When it comes to teams working with many servers, deploying a bastion host (jump box) may be a clean and effective way to solve the long-term problem. With this method, you only expose SSH to the bastion, and the other servers accept it only when it’s from the bastion’s internal IP. This centralizes logging and makes auditing access far simpler.
Using a virtual private network (VPN) and a bastion host together is perfectly fine – and many solutions use both: a safe way to access the private network via a VPN, followed by use of a bastion host to restrict which servers can be accessed. Some teams may decide to forgo the bastion because they don’t have the manpower to manage one, and so use a combination of a VPN and a set of firewall rules that still quite a bit lowers the exposure, but without the extra effort.
Mistakes Leading to Leaving Cloud Servers Open
The Mistakes That Cause Leaving Cloud Servers Open: Even the safest development teams may have slip-ups from time to time. One of the most frequent is leaving staged, or test servers with relaxed firewall rules equivalent to those of the production environment – hackers don’t concern themselves with which environment they first land on. Another frequent error is reusing the same SSH key on several servers and clients, causing one hacked laptop to compromise all servers that key has access to.
Another common human error is not removing or changing access when someone leaves the team, so stale credentials remain valid and accessible. At last, putting trust in the strategy of “security through obscurity” – meaning one thinks that setting up the unusual port or hiding the hostname from the public is actually sufficient security – creates a wrong impression of security. This is mostly true; in reality, modern-day attackers scan all ports anyway, and there is no way to hide from them.
System Administrators Guide to Secure Remote Access
Prohibit SSH password logins totally and depend exclusively on key-based authentication
- Surely no one wants to type in the password every time; because of this, use only key-based authentication
- Deter the user from logging in as root by default and instead use the sudo command to do root tasks
- A firewall or security group rule can provide great help with IP address-based restrictions on SSH logins
- For access that comes from untrusted sources or external networks, use a secure tunnel like a vpn or bastion host
- Periodically change SSH keys and inspect access lists
- Maintain records of login attempts and detect brute-force attacks as quickly as possible
Frequently Asked Questions
By far the biggest reason why this can happen is unauthorized password-based SSH logins that have been cracked by brute force. The scenario is most likely to develop where the administrator allows root login via password and leaves the default port open.
It is true that SSH keys drastically decrease the danger of a successful brute-force attack. However, if there is only key authentication on the server, there are still risks – the server administrator can always enable root login or disable the IP-based login restrictions. So it is recommended to always have these three in the server configuration: disabled root login, restricted access to known IPs, and rotating the keys regularly as the main components of meaningful protection.
A VPN gives extra security by first encrypting your computer traffic before it reaches your network, where the SSH connection will be used. This is mostly important when working on untrusted networks – like public wi-fi – where there is a threat of a potential hacker in your local network looking at your data.
The bastion host works by funneling SSH sessions from many users through a single, carefully monitored server point while the rest of the network (and mostly the servers) remains protected from the internet. At the same time, a vpn will fully encrypt the communication between the user and the corporate network or servers. The combination is very common among larger security teams as a part of the defense-in-depth principle.
The ideal period to change your SSH keys depends on the security practices of your organization, but generally a good practice is to change SSH keys between 90 and 180 days, or in the case that the user who had access with the key leaves or is no longer able to be contacted, such as when a team member leaves.
Changing the port reduces automated scanning noise in your logs but isn’t a real security control on its own — port scanners check all ports, so it should never replace key-based auth and firewall rules.