Botnet activity explained: how botnets work and how to stop them

What is a botnet?

A botnet is a collection of internet-connected devices that have been infected with malware and are remotely controlled by an attacker, usually without the owner noticing. Each compromised device — a laptop, a server, an office router, a network camera, a smart TV, even a printer — becomes a bot. The person or group operating the collection is the bot herder.

Individually, one infected laptop in Road Town is a minor nuisance. Combined with tens of thousands of others, it becomes rented infrastructure: bandwidth, processing power, credentials and clean-looking IP addresses that criminals sell by the hour. That is what makes botnets the backbone of commercial cyber crime, and why an infection on a single machine is a business problem rather than a user problem.

Public botnet maps and live threat maps visualise this activity as arcs of attack traffic crossing the globe. They are a useful illustration of scale, but they cannot tell you whether your devices are part of it. Only monitoring inside your own network can do that.

How botnets operate

Almost every botnet follows the same four-stage lifecycle. Understanding the stages matters because each one gives you a separate opportunity to break the chain.

1. 1. Recruitment

   Automated scanners sweep the internet for an unpatched service, an exposed remote desktop port, a default password on a router or camera, or a user who opens a malicious attachment or clicks a phishing link. No targeting decision is made — if the door is open, the device is taken.

2. 2. Infection and persistence

   A small loader installs the bot software, disables or blinds security tools, and creates persistence through scheduled tasks, services, registry keys or start-up items so it survives a reboot. Many loaders then pull down additional payloads on demand.

3. 3. Command and control (C2)

   The bot phones home to a controller — a hosted server, a peer-to-peer mesh, a hijacked website, or even a chat or social media channel — to collect instructions. Domain-generation algorithms and encrypted traffic are used to make this channel hard to block.

4. 4. Monetisation

   The herder issues one command and the whole fleet acts: flood a target, send spam, harvest saved passwords, mine cryptocurrency, proxy someone else's traffic, or drop ransomware. Access is frequently resold to other criminal groups.

Common botnet attack methods

Ransomware deserves particular attention because it is so often the final act of a botnet infection. Read our ransomware guidance for what to do in the first hour of an incident.

Why this is a business risk, not just an IT issue

• Downtime

  Staff idle and customers unable to transact while services are flooded or systems are rebuilt.

• Email deliverability

  A blocklisted domain means quotes, invoices and statements silently stop arriving.

• Financial loss

  Fraudulent payments, ransom demands, incident response costs and overtime.

• Data exposure

  Client and employee data leaving the business creates legal and contractual consequences.

• Reputation

  Being the source of attack traffic against a partner is a difficult conversation to have.

• Insurance and compliance

  Cyber policies and client due-diligence questionnaires increasingly require demonstrable controls.

Island businesses carry an extra burden: bandwidth is a finite, expensive resource, and specialist help is not always on the next flight. Prevention and early detection are considerably cheaper here than recovery.

Signs your devices may be part of a botnet

• Outbound traffic or bandwidth spikes overnight or at weekends when nobody is working.
• Machines that run hot, noisy or slow with no obvious workload.
• Your domain or public IP address appearing on an email blocklist, or partners reporting spam from you.
• Antivirus, endpoint protection, Windows Update or logging silently disabled.
• Bursts of failed sign-ins to Microsoft 365 or the VPN from unfamiliar countries.
• New scheduled tasks, services, browser extensions or start-up entries nobody created.
• Firewall or DNS logs showing repeated connections to newly registered or randomly named domains.
• Users reporting password resets, mailbox rules or sent items they did not create.

Any one of these on its own can be innocent. Two or three together should trigger an investigation rather than a reboot — rebuilding one machine while the C2 channel is still open simply invites reinfection.

Cyber security best practices that break the chain

1. Patch quickly and completely. Operating systems, browsers, third-party applications and — critically — firmware on routers, firewalls, NAS units and cameras. Unmanaged network devices are the most common recruits.
2. Enforce multi-factor authentication everywhere. Especially Microsoft 365, VPN and remote access. MFA neutralises the stolen credentials botnets trade in.
3. Deploy monitored endpoint detection and response. Signature antivirus alone does not see a quiet C2 beacon. Detection plus someone watching the alerts is what shortens dwell time.
4. Filter DNS and egress traffic. Blocking known C2 and newly registered domains stops the malware from ever receiving instructions.
5. Remove standing administrator rights. Most loaders need elevation to persist. Standard user accounts stop many infections dead.
6. Segment the network. Keep guest Wi-Fi, IoT devices and servers apart so one recruited camera cannot reach your finance systems.
7. Keep tested, offline or immutable backups. The control that turns a ransomware event from a crisis into an inconvenience.
8. Train your people continuously. Phishing remains the primary delivery route, and AI-written lures are markedly more convincing than they used to be.
9. Have a written incident response plan. Know in advance who isolates devices, who calls whom, and where the recovery documentation lives.
10. Review and audit regularly. Exposed ports, dormant accounts and forgotten devices accumulate quietly between projects.

Structured frameworks help you prove the basics are in place — see cyber fundamentals, Cyber Essentials and cyber awareness training for staff.

How Fresh Mango helps businesses reduce cyber risk

Fresh Mango Technologies has supported businesses across the British Virgin Islands and the wider Caribbean for over 15 years, with engineers based in Tortola and a UK team behind them. Our approach to botnet risk is deliberately unglamorous: close the doors, watch the traffic, and be ready to respond.

• Managed patching and device hygiene→
• Cyber security services and hardening→
• Microsoft 365 security and MFA rollout→
• Backup, offsite and offline recovery→
• Staff cyber awareness training→
• Free cyber security health check→

Botnet FAQs

What is a botnet in simple terms?

A botnet is a network of internet-connected devices — PCs, servers, routers, cameras, phones — that have been infected with malware and are quietly controlled by a criminal operator. Each infected device is a 'bot'. The operator issues one instruction and thousands of machines obey at once.

How would I know if a company device has joined a botnet?

Typical signs are unexplained outbound traffic at night, machines running hot or slow, your domain or IP address appearing on an email blocklist, security tools being switched off, sudden spikes in failed logins, and new scheduled tasks or start-up entries nobody created.

Are small Caribbean businesses really targeted by botnets?

Yes. Botnet recruitment is automated and indiscriminate — scanners look for an exposed service or an unpatched device, not for a well-known brand. Smaller organisations are often easier to recruit because patching, monitoring and multi-factor authentication are weaker.

What is the single most effective defence against botnets?

There is no single control, but the highest-value combination is fast patching, multi-factor authentication on every account, and monitored endpoint detection and response so an infection is spotted and isolated in minutes rather than months.