What is a Botnet Attack?
A botnet attack is a type of cyber attack carried out by a group of internet-connected devices controlled by a malicious actor.
Botnets themselves are simply the network of devices. It is when cyber criminals inject malware into the network to control them as a collective that they get used for launching cyber attacks. Botnet attacks can be used for sending spam, data theft, compromising confidential info, perpetuating ad fraud or for launching more dangerous Distributed Denial of Service or DDoS攻撃.
Bot Attacks vs a Botnet Attack
Botnet attacks can be thought of as a specific type of the more general “bot attack”. Bot attacks are cyber attacks that use automated web requests meant to tamper with a website, application or device.
Bot attacks initially consisted of simple spamming operations but have evolved to be more complex in nature, intended to defraud or manipulate users. One of the reasons for this is the availability of open-source tools for building bots, known as botkits.
These botkits, usually available for free online or on the Dark Web, can be used to carry out nefarious tasks like scraping a website, taking over an account, abusing form submissions and to create botnet attacks, including DDoS attacks.
How Does a Botnet Attack Work?
Botnet attacks start with cyber criminals gaining access to devices by compromising their security. They could do this via hacks like the injection of Trojan viruses or basic social engineering tactics. Then these devices are brought under control using software that commands the devices to carry out attacks on a large scale.
Sometimes, the criminals themselves may not use the botnet to launch attacks but instead, they sell access to the network to other malicious actors. These third parties can then use the botnet as a “zombie” network for their own needs, like directing spam campaigns.
The Different Types of Botnets
Botnet attacks can differ based on their methods and the tools they employ. Sometimes these botnets themselves don’t attack but instead become a pathway for hackers to launch secondary campaigns like scams and ransom attacks. Some of the common types of botnet attacks include:
- Distributed Denial-of-Service (DDoS) attacks: One of the more common types of botnet attacks which work by overloading a server with web traffic sent by bots in order to crash it. This downtime in the server’s operation can also be used for launching additional botnet based attacks.
- Phishing attacks: These are often launched with the purpose of extracting key information from an organization’s employees. For example, mass spam campaigns can be devised to imitate trusted sources within the organization to trick people into revealing confidential information like login details, financial info and credit card details.
- Brute force attacks: These involve programs which forcefully breach web accounts by force. Dictionary attacks and credential stuffing are used to exploit weak user passwords and access their data.
What Systems & Devices are Most at Risk?
When botnet attacks make the news, the damages are usually referred to as the number of computers or servers that are compromised. But it’s not just individual systems that can be infected and brought down. Any device that is connected to the internet is vulnerable to botnet attacks.
With the growth of IoT, more devices are joining the internet, increasing the attack vector possibilities. Even the seemingly harmless wireless CCTV cameras that watch your porch or backyard can be compromised to open an entry point for botnet malware to enter the network. The fact that such new IoT devices can come with poorly configured security settings only worsens the problem.
Detecting Botnet Attacks
Botnet attacks are hard to detect because the user is often not aware when a device is compromised. Some botnets are designed with a central server controlling each bot in a command-and-control model. For these botnets, a key step to detecting attacks involves finding that central server.
Static analysis techniques can be helpful to spot infections in devices. These are run when the device is not executing any programs and involve looking for malware signatures and other suspicious connections to command-and-control servers that look for instructions and suspicious executable files. As botnet creators develop more sophisticated techniques to avoid detection, they are increasingly becoming better at avoiding static analysis methods.
Behavioural or dynamic analyses can also be used if there are more resources available. These involve scanning ports on local networks, looking for unusual traffic and activity involving Internet Relay Chat (IRC).
Antivirus software can detect botnet attacks to a certain extent but fails to spot infected devices. Another interesting method is using honeypots. These are fake systems that bait a botnet attack via a fake infiltration opportunity.
For larger botnets, like the Mirai botnet, ISPs sometimes work together to detect the flow of traffic and figure out how to stop the botnet attack. They could work with security firms to identify other compromised devices in the network.
Can Botnet Attacks be Prevented?
Preventing botnet attacks has become more difficult over the years. One of the main challenges in preventing these attacks is the proliferation of devices. As different types of devices become easily available, often with their own security settings, it becomes difficult to monitor, track and stop these attacks before they happen. Yet you can still take certain measures to prevent botnet attacks.
- Keep all systems updated
One of the main pathways that botnets take to penetrate and compromise a business’ security system is using the unpatched vulnerabilities present in the network’s machines. This makes it critical to keep the systems updated, and to ensure new updates are installed as soon as they are available.
This also includes hardware devices, especially legacy devices which can often be ignored in enterprises when they are no longer used actively.
- Adopt basic cybersecurity best practices
It is important to follow basic security hygiene on all devices as well, to keep botnet attacks at bay. This involves using complex passwords, educating employees about the dangers of phishing emails and clicking on suspicious attachments and links. Enterprises should also take appropriate measures to ensure that any new device that enters their network has sound security settings.
- Control access to machines
Taking measures to lock access to machines is another way you can prevent botnet attacks. In addition to strong passwords, you should also deploy multi-factor authentication and controls to provide access to only those who need it most. If access to critical systems are controlled and separated from each other, it becomes slightly easier to isolate botnet attacks to a specific set of devices and to eradicate them there.
- Monitor network traffic using analytics solutions
Prevention of botnet attacks requires good techniques to detect them ahead of time. Using advanced analytics to monitor and manage traffic flows, user access and data leaks is another measure you can take. The Mirai botnet was one such instance where the attackers exploited insecure connected devices.
How to Mitigate Against Bot Attacks
Sometimes even your best prevention measures can be overcome by botnet attacks, and it becomes too late by the time you detect them in your network. In such scenarios, your best bet is to mitigate the impact of such attacks. This means reducing the damage that will be caused.
- Disable the central server
Botnets designed in the command-and-control model can be disabled if the central resource or server is identified. Think of it like cutting off the brain of the operation to take down the whole botnet.
- Run antivirus or reset the device
For individual computers which have been compromised, the goal should be to regain control. And this can be done by running antivirus software, reinstalling the system’s software or reformatting the system from scratch. In the case of IoT devices, you will have to flash the firmware, completing a factory reset to mitigate a botnet attack.