How Much CPU Does a Brute Force Attack Actually Consume?

Many people think password guessing attacks are only a problem if someone actually gets the password right. But the reality is worse: the sheer volume of failed attempts slows down your server – even when none of the passwords are correct.

What Is a "Brute Force" Attack?

Simply put: guessing passwords by raw force. Imagine someone standing at your door with a huge ring of keys, trying each one to see if it fits the lock. No tricks, no cleverness – just trying again and again, thousands or tens of thousands of times. Of course, no person does this by hand – a program does it automatically, sometimes hundreds of times per minute.

What Does This Look Like in Practice?

Imagine your server is a reception desk where employees are checked in. Normally, the receptionist works calmly – lets in familiar faces, everything runs smoothly.

Now imagine that thousands of strangers line up every day, each trying to get in with a fake ID. The receptionist has to check each one, turn them away, and write it down. Meanwhile, the real employees are stuck waiting in line too.

This is exactly what happens to your server during a password guessing attack. Every fake login attempt is work for the machine: it has to check it, reject it, and log it. And this isn't ten or twenty attempts – it's thousands, every single day.

How Much Does It Slow Things Down?

An unprotected server can receive 5,000–10,000 fake login attempts per day. That means a significant portion of your machine is busy doing useless work.

The result:

• The server gets slower – applications, websites, and remote desktop connections respond more sluggishly
• Less power for real work – it's as if someone else is using part of your machine, except they're not doing anything useful with it
• Logs fill up – the system log fills with junk entries, and when something important actually happens, it's harder to find

It's Like Someone Constantly Knocking on Your Door

The biggest problem isn't any single attempt – it's that it never stops. Day and night, weekends, holidays – the attempts keep coming. Your machine never rests, constantly doing pointless work.

Users feel this too: remote desktop is slower, things take longer to open, and sometimes the server seems to be "thinking." But it's not thinking – it's busy rejecting intruders by the thousands.

How Does BruteFence Solve This?

BruteFence works simply: if someone tries the wrong password too many times, it automatically blocks them. No need to reject the same attacker a thousand times – after the first few attempts, they can't even get in line anymore.

The effect is immediate:

• The server gets its performance back because it's not wasting effort on junk requests
• Applications and remote desktop respond faster
• Logs stay clean and easier to read
• The server is freed up, so its full capacity can go toward actual tasks

The difference is clear: without protection, the server processes thousands of pointless attempts every day. With BruteFence, it stops after just a few tries.

Check If This Affects You

If you're curious whether your server is dealing with this:

1. Open Event Viewer
2. Go to Windows Logs → Security
3. Search for Event ID 4625 – these are failed login attempts
4. Check how many there have been in the last 24 hours

If you see numbers in the hundreds or thousands – your machine is constantly working for nothing.

Summary

A password guessing attack doesn't just risk someone getting in – it also continuously drains your server's performance. It's like a dripping tap: each drop seems like nothing, but the water bill adds up. BruteFence fixes this: it automatically blocks the attackers, so your server can finally focus on what it's supposed to – real work.

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Read our related articles:

• Event ID 4625: What It Means and What to Do
• What Is an RDP Brute Force Attack?

Try BruteFence free for 7 days — installs in 5 minutes, then protects automatically. Download →