Ad & Malicious Domain Blocking

PRX-SD includes a built-in adblock engine that blocks ads, trackers, and known malicious domains at the DNS level by writing entries to the system hosts file (/etc/hosts on Linux/macOS, C:\Windows\System32\drivers\etc\hosts on Windows). Filter lists are stored locally under ~/.prx-sd/adblock/ and support both Adblock Plus (ABP) syntax and hosts-file format.

How It Works

When you enable adblock, PRX-SD:

1. Downloads configured filter lists (EasyList, abuse.ch URLhaus, etc.)
2. Parses ABP rules (||domain.com^) and hosts entries (0.0.0.0 domain.com)
3. Writes all blocked domains to the system hosts file, pointing them to 0.0.0.0
4. Logs every blocked domain lookup to ~/.prx-sd/adblock/blocked_log.jsonl

TIP

For full DNS-level filtering with upstream forwarding, combine adblock with the DNS proxy. The proxy integrates adblock rules, IOC domain feeds, and custom blocklists in a single resolver.

Commands

Enable Protection

Download filter lists and install DNS blocking via the hosts file. Requires root/administrator privileges.

sudo sd adblock enable

Output:

>>> Enabling adblock protection...
  Loaded 4 lists (128432 rules)
success: Adblock enabled: 95211 domains blocked via /etc/hosts
  Lists: ["easylist", "easyprivacy", "urlhaus-domains", "malware-domains"]
  Log: /home/user/.prx-sd/adblock/blocked_log.jsonl

Disable Protection

Remove all PRX-SD entries from the hosts file. Credentials and cached lists are preserved.

sudo sd adblock disable

Sync Filter Lists

Force re-download all configured filter lists. If adblock is currently enabled, the hosts file is automatically updated with the fresh rules.

sudo sd adblock sync

View Statistics

Display the current status, loaded lists, rule count, and block log size.

sd adblock stats

Output:

Adblock Engine Statistics
  Status:        ENABLED
  Lists loaded:  4
  Total rules:   128432
  Cache dir:     /home/user/.prx-sd/adblock
  Last sync:     2026-03-20T14:30:00Z
  Blocked log:   1842 entries

  - easylist
  - easyprivacy
  - urlhaus-domains
  - malware-domains

Check a URL or Domain

Test whether a specific URL or domain is blocked by the current filter lists.

sd adblock check ads.example.com
sd adblock check https://tracker.analytics.io/pixel.js

If the domain is not fully qualified with a scheme, PRX-SD automatically prepends https://.

Output:

BLOCKED ads.example.com -> Ads

or:

ALLOWED docs.example.com

View Block Log

Display recent blocked entries from the persistent JSONL log. The --count flag controls how many entries to show (default: 50).

sd adblock log
sd adblock log --count 100

Each log entry contains a timestamp, domain, URL, category, and source.

Add a Custom Filter List

Add a third-party or custom filter list by name and URL. The --category flag classifies the list (default: unknown).

Available categories: ads, tracking, malware, social.

sd adblock add my-blocklist https://example.com/blocklist.txt --category malware

Remove a Filter List

Remove a previously added filter list by name.

sd adblock remove my-blocklist

Default Filter Lists

PRX-SD ships with the following built-in filter sources:

List	Category	Description
EasyList	Ads	Community-maintained ad filter list
EasyPrivacy	Tracking	Tracker and fingerprinting protection
URLhaus Domains	Malware	abuse.ch malicious URL domains
Malware Domains	Malware	Known malware distribution domains

Filter List Format

Custom lists can use either Adblock Plus (ABP) syntax or hosts-file format:

ABP format:

||ads.example.com^
||tracker.analytics.io^

Hosts format:

0.0.0.0 ads.example.com
127.0.0.1 tracker.analytics.io

Lines starting with !, #, or [ are treated as comments and ignored.

Data Directory Structure

~/.prx-sd/adblock/
  enabled           # Flag file (present when adblock is active)
  config.json       # Source list configuration
  blocked_log.jsonl # Persistent block log
  lists/            # Cached filter list files

WARNING

Enabling and disabling adblock modifies your system hosts file. Always use sd adblock disable to cleanly remove entries rather than editing the hosts file manually. The command requires root/administrator privileges.

Examples

Full setup workflow:

# Enable with default lists
sudo sd adblock enable

# Add a custom malware blocklist
sd adblock add threatfox-domains https://threatfox.abuse.ch/export/hostfile/ --category malware

# Re-sync to download the new list
sudo sd adblock sync

# Verify a known malicious domain is blocked
sd adblock check malware-c2.example.com

# Check stats
sd adblock stats

# View recent blocks
sd adblock log --count 20

Disable and clean up:

sudo sd adblock disable

Next Steps

• Set up the DNS Proxy for full DNS-level filtering with upstream forwarding
• Configure Webhook Alerts to get notified when domains are blocked
• Explore the CLI Reference for the full command list