---
title: "Custom Fail2ban Jail: Apache Directory Scanning & Junk Methods"
domain: troubleshooting
category: security
tags: [fail2ban, apache, security, bots, wordpress]
status: published
created: 2026-04-02
updated: 2026-04-02
---
# Custom Fail2ban Jail: Apache Directory Scanning & Junk Methods

## 🛑 Problem

Bots and vulnerability scanners enumerate WordPress directories (`/wp-admin/`, `/wp-includes/`, `/wp-content/`), probe for access-denied paths, or send junk HTTP methods (e.g., `YQEILVHZ`, `DUTEDCEM`). These generate Apache error log entries but are not caught by any default Fail2ban jail:

- `AH01276` — directory index forbidden (autoindex:error)
- `AH01630` — client denied by server configuration (authz_core:error)
- `AH00135` — invalid method in request (core:error)

The result is a low success ratio on Netdata's `web_log_1m_successful` metric and wasted server resources processing scanner requests.

---

## ✅ Solution

### Step 1 — Create the filter

Create `/etc/fail2ban/filter.d/apache-dirscan.conf`:

```ini
# Fail2ban filter for Apache scanning/probing
# Catches: directory enumeration (AH01276), access denied (AH01630), invalid methods (AH00135)

[Definition]
failregex = ^\[.*\] \[autoindex:error\] \[pid \d+\] \[client <HOST>:\d+\] AH01276:
            ^\[.*\] \[authz_core:error\] \[pid \d+\] \[client <HOST>:\d+\] AH01630:
            ^\[.*\] \[core:error\] \[pid \d+\] \[client <HOST>:\d+\] AH00135:

ignoreregex =
```

### Step 2 — Add the jail

Add to `/etc/fail2ban/jail.local`:

```ini
[apache-dirscan]
enabled = true
port = http,https
filter = apache-dirscan
logpath = /var/log/apache2/error.log
maxretry = 3
findtime = 60
```

Three hits in 60 seconds is aggressive enough to catch active scanners while avoiding false positives from legitimate 403s.

### Step 3 — Test the regex

```bash
fail2ban-regex /var/log/apache2/error.log /etc/fail2ban/filter.d/apache-dirscan.conf
```

This shows match counts per regex line and any missed lines.

### Step 4 — Reload Fail2ban

```bash
fail2ban-client reload
fail2ban-client status apache-dirscan
```

---

## 🔍 What Each Pattern Catches

| Error Code | Apache Module | Trigger |
|---|---|---|
| `AH01276` | `autoindex:error` | Bot requests a directory with no index file and `Options -Indexes` is set. Classic WordPress/CMS directory enumeration. |
| `AH01630` | `authz_core:error` | Request denied by `<Directory>` or `<Location>` rules (e.g., probing `/wp-content/plugins/`). |
| `AH00135` | `core:error` | Request uses a garbage HTTP method that Apache can't parse. Scanners use these to fingerprint servers. |

---

## 🔁 Why Default Jails Miss This

| Default Jail | What It Catches | Gap |
|---|---|---|
| `apache-badbots` | Bad User-Agent strings in access log | Doesn't look at error log; many scanners use normal UAs |
| `apache-botsearch` | 404s for common exploit paths | Only matches access log 404s, not error log entries |
| `apache-noscript` | Requests for non-existent scripts | Narrow regex, doesn't cover directory probes |
| `apache-overflows` | Long request URIs | Only catches buffer overflow attempts |
| `apache-invaliduri` | `AH10244` invalid URI encoding | Different error code — catches URL-encoded traversal, not directory scanning |

The `apache-dirscan` filter fills the gap by monitoring the error log for the three most common scanner signatures that slip through all default jails.

---

## ⚠️ Key Notes

- **`logpath` must point to the error log**, not the access log. All three patterns are logged to `error.log`.
- **Adjust `logpath`** for your distribution: Debian/Ubuntu uses `/var/log/apache2/error.log`, RHEL/Fedora uses `/var/log/httpd/error_log`.
- **The `allowipv6` warning** on reload is cosmetic (Fail2ban 1.0+) and can be ignored.
- **Pair with `recidive`** to escalate repeat offenders to longer bans.

---

## 🔎 Quick Diagnostic Commands

```bash
# Test filter against current error log
fail2ban-regex /var/log/apache2/error.log /etc/fail2ban/filter.d/apache-dirscan.conf

# Check jail status
fail2ban-client status apache-dirscan

# Watch bans in real time
tail -f /var/log/fail2ban.log | grep apache-dirscan

# Count current error types
grep -c "AH01276\|AH01630\|AH00135" /var/log/apache2/error.log
```