What is a Botnet?

A botnet is a network of malware-infected devices used to launch coordinated attacks either against a single target, like during a DDoS attack, or multiple targets like during email phishing attacks.

All infected machines in a botnet are remotely controlled by a single cyber attacker that could be located anywhere in the world.

Any internet-facing device capable of being infected by malware can be used in a botnet, including Internet of Things devices (IoT devices), computers, servers, and even mobile devices.

The addition of each compromised device to a botnet compounds the intensity of a botnet attack, so the larger the number of infected devices in a botnet the more devastating the cyberattack will be.

Examples of Botnet Attacks

Botnets (short for 'robot networks') are commonly used for the following cyberattacks:

Botnet Attack Example: DDoS Attacks

A DDoS attack (Distributed Denial of Service attack) is when a botnet is used to direct a high number of connection requests at a web server or private network to overload it and force it offline. 

Multiple computer devices sending fake traffic to a server

A DoS attack is executed by a single compromised device. DDoS attacks, on the other hand, are executed with multiple compromised devices to maximize damage.

Dos vs DDoS attack

DDoS attacks are sometimes launched to disrupt website sales for a competitive advantage. Like ransomware, DDoS attacks can also be used for extortion purposes, where a victim is forced to make a payment to cease the cyberattack.

Regardless of the motive, all forms of DDoSing are illegal.

Signs you might be a victim of a DDoS attack

There are two signs that could be indicative of a DDoS attack taking place.

1. Your website is loading slowly

If your website is loading unusually slowly, it could be because your web server is under attack. This is likely to be the case if your website eventually stops loading completely and instead displays a ‘503 service unavailable’ error.

2. You see a ‘503 service unavailable’ error when you try to load your website

503 service unavailable error
503 service unavailable error

If other websites load perfectly but you see a ‘503 service unavailable’ message when you try to load your website, it means your web server is incapable of loading your website. This is the intended outcome of a DDoS attack.

Botnet Attack Example: Phishing Attacks

A phishing attack is when cybercriminals send seemingly innocuous emails that contain infected links with the intention of stealing private credentials to access sensitive data.

A botnet can launch a large-scale phishing attack to increase the chances of recipients falling for the email trickery.

Signs you might be targeted in a phishing attack

The following signs could be indicative of phishing attempts. If you receive any emails with these characteristics, do not interact with them.

If you believe you are a victim of a phishing attack, you can report each instance to the relevant authority.

  • Phishing emails - Can be forwarded to the Federal Trade Commission at spam@uce.gove and to the Anti-Phishing Working Group (APWG) at reportphishing@apwg.org.
  • Phishing text messages - Can be forwarded to the number 7726 (SPAM).  

Botnet Attack Example: Financial Data Breaches

Financial botnets target financial institutions to breach sensitive financial information like credit card numbers.

A Zeus botnet is an example of a very sophisticated type of financial botnet. The GameOver Zeus malware is spread through phishing emails. Infected computers are searched for banking credentials which are then used to redirect funds to criminal accounts.

Shutting down a GameOver botnet is not easy because the network is built upon a peer-to-peer command and control infrastructure. With this arrangement, malicious instructions are sent to each infected computer from other compromised devices on the botnet, rather than from a fixed location.

The GameOver Zeus botnet is estimated to be responsible for more than $100 million in losses.

Signs You Might be Infected by Zeus Malware

If you experience any of the following symptoms, your computer may be infected by Zeus malware. For instructions on how to remove GameOver Zeus malware, refer to these instructions by the Cybersecurity & Infrastructure Security Agency (CISA).

  • Your cursor moves independently.
  • Your computer is significantly slower than usual.
  • You notice suspicious financial activity in your bank statements.
  • You notice text-based chat windows on your desktop.

Botnet Attack Example: Targeted Intrusions

A targeted intrusion is when botnets are used to achieve data breaches. During these attacks, a specific point of a network is targeted and compromised so that attackers can intrude deeper into sensitive resources.

Signs You Might Be a Victim of a Targeted Intrusion

A sign of a targeted intrusion is multiple connection requests from the same IP address to a single server port, which is also the sign of a DDoS attack.

Instead of manually referring to web server logs, these cyberattacks can be detected more efficiently with honeytokens strategically placed around sensitive resources.

How Do Botnets Work?

A botnet is created when internet-facing devices infected with a specific malware are networked together. Computers are the primary devices in a botnet and the malware that infects them is either injected from a phishing email, a compromised website, or a click fraud campaign.

PCs are the primary computer targets of botnet malware. Though Macs are not immune, they have a significantly lower chance of being compromised. 

IoT devices can also become bots. In late 2016, malware known as Mirai infected 600,000 Linux CCTV cameras. The Mirai botnet launched a DDoS attack that was so big, it caused an internet outage for half of the U.S East Coast

Once infected, each compromised device clandestinely connects to criminal servers - known as Command and Control Servers - so that they can be remotely controlled by threat actors to orchestrate botnet attacks.

Cybercriminals can connect to their botnets in two architectural arrangements:

Botnet Arrangement 1: Client-Server Model

The client-server model is the most common botnet arrangement. Each infected device connects to a criminal Command and Control server (C&C server) that issues commands to the botnet through one of two communication protocols - IRC (Internet Relay Chat), or HTTP (HyperText Transfer Protocol).

client-server model

Botnet Arrangement 2: P2P Model

Unlike a client-server botnet model, the P2P botnet model is decentralized, meaning commanding instructions are not sent from a single static source. Instead, each compromised device can send instructions to other bots on the network. 

P2P model

The aforementioned Zeus malware operates under this architecture.

Botnet malware is designed to discover devices with vulnerable endpoints so that new bots can be instantly recruited without having to contend with cyber defenses or human barriers.

Rapid autonomous expansion is the primary objective of botnet campaigns.

What's most concerning about botnet recruitment is that victims are usually unaware that their devices have been compromised. A botnet infection could last for many years before it's discovered - if it ever is.

Newly recruited bots remain dormant until they receive commands from a bot herder or botmaster - which is either another compromised device in a P2P botnet or the central command server in a client-server botnet.

Even when activated, botnets operate without any noticeable evidence. Each bot only diverts a small portion of a victim's bandwidth at a specified target. This process happens quietly in the background, hidden behind legitimate computer tasks.

Because each bot only compromises a small amount of processor bandwidth, botnets need to be vast to achieve the necessary degree of malicious traffic required to launch a cyberattack.

8 Signs Your Computer is Part of a Botnet

With careful attention to detail, it's possible to detect if your computer has been recruited into a botnet.

The more signs you notice, the higher the chances that your computer is a bot.

1. You Cannot Update your Computer

Software updates protect your programs from the latest cyber threats. Botnet malware could be programmed to block operating system updates to prevent being outed by the latest software patches.

A critical sign that you're likely infected by botnet malware is if you cannot download antivirus software updates.

2. Your Fan Operates Loudly When Your Computer is Idle

It doesn't make sense for your fan to increase speed when you're using fewer resources. It could be evidence that cybercriminals are leveraging the extra bandwidth availability to increase the intensity of a botnet attack.

Before settling with this conclusion, check whether any software updates are being installed in the background and whether your computer fan is burdened with excessive dust.

Also, look for any other accompanying signs from this list.

3. Programs are Unusually Slow

This could be a sign of a computer in great need of a service or it could be evidence that hidden malicious programs are using most of your computer's processing bandwidth.

4. Your Computer Shuts Down Very Slowly

Botnet malware could prevent computers from shutting down at a usual speed in order to mitigate interference with malicious background activities.

5. Your Facebook Has Been Hacked

Once infected, bots are instructed to seek out other devices to infect. Sometimes this involves hacking a victim's social media accounts and sending theirfriends messages with malware-infected links. 

Each friend that interacts with such links is added to the botnet, which then exploits their Facebook friends list, continuing the pernicious attack cycle. 

This is why it's best cybersecurity practice to end each social media session by logging out, and not by just closing the browser.

6. Your Email Contacts Have Received an Email From Your Account That You Never Sent

Just like with your social media accounts, botnet malware could also use your email account to spread the infection to other computers. This is why you should always log out of your email after each session and not just close the browser.

7. Your Internet Speed is Unusually Slow 

A slow internet connection could be a sign that your computer is participating in a botnet attack.

8. You Notice Suspicious Activity in your Task Manager

An example of suspicious activity is unrecognizable programs using high amounts of disk resources. To check if this is happening, open Task Manager then click on the Disk tab to sort programs by highest disk usage. 

A high disk resource rate is about 3-5MB/s. If you don't recognize the program requiring this level of bandwidth, search its name in Google to confirm it's not a critical process you shouldn't close. If not, immediately terminate the program.

What to Do if You're Infected with Botnet Malware

If your computer has been recruited into a botnet, the immediate course of action should be to sever the botnet communication channel by cutting your internet connection. 

If the botnet malware prevents you from toggling the Wifi switch on your computer, unplug your router.

Once this has been done, you will need to contact a computer support specialist to reinstall a clean version of your operating system and notify your local law enforcement of the cyberattack.

8 Ways to Protect Yourself From Botnet Malware

To prevent your devices from botnet malware infection, follow these tips.

1. Close or Filter Unused Ports

An open port could allow cybercriminals to identify application vulnerabilities that could be exploited to inject botnet malware. To prevent this, ensure all unnecessary ports are either completely closed or filtered.

You can use free open port scanners to determine the level of recognizance intelligence cybercriminals could gather about your open ports.

2. Implement Segmentation

Segmentation creates a security premier around vulnerable devices to prevent botnet malware from spreading to other areas of your network. This network security control is especially important for IoT devices.

3. Keep all IoT Devices and Computer Programs Updated

Software updates remediate vulnerabilities being exploited to inject botnet malware and spyware. Regular software updates and firmware updates will keep all remote devices and IoT devices protected.

To prevent overlooking the latest security updates, you should enable automated patches for your web browser and operating system.

4. Use Antivirus Software

Some antivirus software is capable of detecting Zeus malware and other types of malware. To ensure your antivirus is capable of detecting the latest threats, be sure to keep it updated.

Mobile devices can also be used in a botnet attack. Make sure your antivirus software is capable of protecting Android and iOS devices.

4. Use a Firewall

Firewall security controls could detect and block botnet communications with your devices and prevent your resources from being used for cybercrime.

5. User Strong Login Credentials

The best form of botnet malware defense is by keeping cybercriminals out of your private network. Strong user credentials will prevent hackers from gaining access through typical login compromise methods such as brute force attacks.

6. Use Multi-Factor Authentication

Multi-Factor Authentication (MFA) adds an additional complication around your private network should a cybercriminal overcome one of your outer security controls. For the highest level of security, MFA should be spread across different devices and never used on only one system.

7. Never Interact with Suspicious Emails

Phishing attacks are one of the most common methods of spreading botnet malware. If you're suspicious of an email, never investigate by clicking its links or opening attachments.

Even emails from friends and colleagues could be used in phishing attacks. If you're ever suspicious, contact the sender directly by either composing a new email or texting them to confirm legitimacy.

If you cannot confirm the email's security with the sender and you need to click on a link, it's more secure to manually type the address in the URL field to prevent DNS cache poisoning.

8. Use a Pop-Up Blocker

Advertising pop-ups could activate an unsolicited malware download if they are clicked. Simply ignoring all pop-ups isn't a secure solution because most are developed to intentionally surface within the primary clicking area to maximize the chances of an accidental interaction. 

For the best security, a pop-up blocking solution should be implemented.

8. Use an Attack Surface Monitoring Solution

An attack surface monitoring solution will detect any vulnerabilities in your ecosystem that could facilitate a botnet malware injection.

10. Detect and Shut Down Data Leaks

Data leaks are involuntary exposures of sensitive credentials. If discovered by cybercriminals, data leaks could provide a level of network access necessary to inject botnet malware.

When adopting a data leak detection solution, it's important to choose one that's also capable of monitoring the entire vendor network to prevent infection from a third-party breach.

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