Planisys Cybersecurity

Q: How do IoT botnets recruit devices?

Most IoT botnets recruit devices through automated scanning and exploitation of weak credentials or vulnerabilities.

Q: Can DNS detect IoT botnet infections?

Yes. DNS queries to command and control domains often provide early infection indicators.

Q: Why are IoT devices attractive to botnets?

IoT devices are numerous, often poorly secured and continuously connected to the Internet.

Q: Can blocking DNS domains stop IoT botnets?

Blocking command domains can prevent malware communication and limit botnet functionality.

Stage 1 — Device discovery

Attackers continuously scan the Internet searching for vulnerable IoT devices.

Typical discovery methods:

Internet-wide scanning
Shodan-style reconnaissance
Masscan style scanning
Telnet probing
SSH probing
Web interface probing

This phase usually produces no visible DNS activity because attackers are identifying targets.

Stage 2 — Exploitation

Common infection techniques include:

Default credentials
Weak passwords
Firmware vulnerabilities
Remote code execution flaws
Exposed services

Many IoT infections are fully automated and occur within minutes of exposure.

Stage 3 — Command and control enrollment

After infection the device must contact botnet infrastructure.

This is where DNS becomes visible:

C2 domain resolution
Fallback domain attempts
Dynamic DNS usage
Beaconing traffic

This is often the earliest detection point for DNS monitoring.

Real example: Mirai style botnet behavior

The Mirai botnet demonstrated how rapidly IoT botnets can grow. It scanned the Internet for devices using default credentials and enrolled them into attack infrastructure.

DNS monitoring often revealed:

Command domains
Loader infrastructure
Fallback domains
Infrastructure rotation patterns

Modern IoT botnets follow very similar patterns.

Stage 4 — Persistence

Malware attempts to remain active despite reboots.

Techniques may include:

Startup scripts
Cron modifications
Firmware modification
Repeated reinfection

Some IoT botnets rely on reinfection rather than persistence due to limited device storage.

Stage 5 — Botnet operation phase

Once enrolled devices may perform:

DDoS attacks
Scanning activity
Spam distribution
Credential attacks
Proxy services
Traffic relaying

At this stage DNS may show:

C2 communication
Infrastructure updates
Attack coordination domains

Impact of IoT botnets on ISPs

Outbound DDoS traffic
Abuse complaints
Network reputation damage
Spam blacklisting
Transit cost increases
Customer incident tickets

For ISPs, IoT botnets are not just security issues but operational and reputational risks.

Stage 6 — Infrastructure rotation

Botnet operators frequently rotate infrastructure.

Techniques include:

New domains
Dynamic DNS
Fast flux hosting
Bulletproof hosting

DNS monitoring often detects this through:

New domain queries
Short TTL domains
Domain churn

DNS indicators of IoT botnet infection

Security teams often detect IoT botnets through DNS signals such as:

Queries to newly registered domains
Dynamic DNS providers used by malware
Repeated NXDOMAIN responses
High entropy domains (DGA patterns)
Frequent TXT lookups
Beaconing intervals to C2 domains
Short TTL infrastructure domains

These DNS indicators often appear before other security alerts, making DNS monitoring a valuable early detection control.

Detection engineering approaches

Advanced DNS security platforms detect IoT botnets using:

Shannon entropy analysis
Domain length distribution analysis
Query frequency anomaly detection
Inter-arrival timing analysis
Z-score anomaly detection
Domain generation algorithm detection

These techniques allow early detection of infected devices even before attacks begin.

Where DNS detection works best

DNS can detect infections primarily during:

C2 enrollment
Infrastructure rotation
Beaconing phases

This is why DNS monitoring is often the earliest detection method.

How Protective DNS disrupts IoT botnet lifecycles

Blocking malicious domains can:

Prevent C2 communication
Stop attack coordination
Prevent updates
Neutralize infections

Even when devices remain infected, blocking C2 domains often disables botnet functionality.

Frequently Asked Questions about IoT Botnets

How do IoT botnets recruit devices?

Most botnets use automated scanning to find devices with weak credentials or vulnerabilities.

Do infected IoT devices always show symptoms?

Often no. Many devices continue functioning normally while participating in botnet activity.

Can DNS detect IoT botnet infections?

Yes. DNS queries to command infrastructure often reveal infection early.

Why are IoT devices attractive to botnets?

They are numerous, poorly secured and always online, making them ideal for large-scale attacks.

Can blocking DNS domains stop IoT botnets?

Blocking C2 domains often prevents malware from receiving instructions, limiting its effectiveness.

IoT Botnet Lifecycle