Understanding Network and Node-Level Security at InterServer

When you are managing a website or a server, it is frustrating to run into a connection issue. Sometimes, you might find that your IP address is blocked or that a specific port isn’t working. Usually, this isn’t a random glitch—it is one of our security systems working to keep the network safe.

At InterServer, we use different layers of security depending on the type of service you have. Here is a breakdown of the security systems that might affect your IP connections and how they work.

Shared Hosting Security

If you are on a shared hosting plan, you are sharing a server with other users. Because of this, our security is very proactive to prevent one compromised account from affecting everyone else.

• Local Firewall (CSF): We use the ConfigServer Security & Firewall (CSF). This system watches for “brute force” attacks. If you (or a script you’re running) try to log in with the wrong password too many times, CSF will temporarily block your IP address to prevent a hack.
• Imunify WebShield: Sometimes, when you visit a site, you might see a “Captcha” (a challenge to prove you are human). This happens if WebShield is enabled. It triggers if your IP address has been flagged for abusive behavior in the past, such as being part of a botnet or sending spam. You can learn more about how this technology protects servers in this introduction to WebShield.

KVM VPS Systems

With a KVM Virtual Private Server, you have more control, but there are still safety nets in place at the “host node” (the physical machine that houses your virtual server).

• Host Node Protection: Our physical hardware monitors for extreme brute force attacks. If your VPS is being targeted by an intense SSH attack, our system might block the offending IPs at the node level to keep the network stable. Learn more about node-level SSH protection.
• Internal VPS Security: A fresh KVM install is relatively open. However, if you install a control panel like cPanel or DirectAdmin, those panels will install their own firewalls and brute force protection automatically.

Dedicated Servers

Dedicated servers offer the most freedom, meaning security is largely in your hands, but we provide powerful tools if you need them.

• Hardware Firewall (ACL): By default, the optional hardware firewall in your my.interserver.net portal is disabled. You can enable it to create Access Control Lists (ACLs) that strictly define which traffic is allowed to reach your server. See our guide on hardware firewall rules.
• DDoS Protection (Scrub): For high-risk environments, we offer an “Always-On” DDoS protection service called Scrub. This is an optional purchase that filters out malicious traffic before it ever hits your server. Check out the details on Scrubbing services.

Network-Wide Protections

Regardless of your plan, there are network-level safeguards that protect the entire InterServer infrastructure.

• Automatic DDoS Mitigation: If a massive Distributed Denial of Service (DDoS) attack is detected, our network may automatically route traffic through our “Scrub” system to keep the servers online.
• Port 25 (SMTP) Restrictions: To prevent the network from being blacklisted for spam, we have strict rules regarding Port 25. On many VPS instances, Port 25 is blocked by default to prevent unauthorized mailing. If you have a legitimate need to send mail, review our SMTP support documentation.

What should you do if you are blocked?

If you think your IP has been blocked by mistake, the first step is to check if you can access your site from a different network (like a mobile data hotspot). If you can, your home or office IP is likely blocked by one of the systems mentioned above. You can always reach out to our support team to help identify which system is blocking you and why.