8 types of malicious bots – Threats and prevention

Malicious bots pose significant threats to companies of all sizes, often operating stealthily without detection. These self-propagating malware entities infect their hosts and establish connections to central servers, serving as control centers. They are deployed for various nefarious purposes, including launching DDoS attacks, pilfering sensitive data, and tarnishing reputations. Despite efforts to block all bots, distinguishing between good and bad ones remains challenging.

What kind of damage can these malicious bots inflict?

Foremost, they can severely damage your brand. When customers entrust personal or financial information to your company through online forms or purchases, they rely on your ability to safeguard their data. However, when malicious bots breach this trust and steal data, it jeopardizes your customers and tarnishes your reputation.

Secondly, by inundating your visitors with unwanted download links, malicious bots can lead to your site being blacklisted by search engines. Thirdly, they can disrupt load times, alter content, manipulate backlinks, and even cause website crashes, negatively impacting your SEO ranking.

Moreover, bots can distort your analytics by generating fake traffic data through interactions with your site. They can also manipulate your click-through rate (CTR) by fraudulently clicking on ads, a practice known as click fraud. Beyond ad clicks, advanced bots can populate forms on your site with fake customer information, compromising your database integrity.

If your site’s security measures are inadequate, bots can easily inject malware codes into your HTML headers, enabling them to redirect your traffic to undesired destinations. For instance, the MosQUito jQuery script can hijack traffic from search or paid advertising sources intended for your Joomla or WordPress site and divert it elsewhere.

Types of malicious bots

Let’s delve into some of the nefarious applications of bot technology.

1. SPAM and SPIM bots

Messaging spam, often referred to as SPIM specifically targets users of website-based instant messaging (IM) services, SMS, or private messaging platforms. These bots inundate users’ inboxes with unsolicited instant messages. They are typically identifiable due to their lack of engagement in conversation, opting instead to entice users with clickable links or hooks.


  • Stay vigilant: Don’t click suspicious links or attachments, even from seemingly familiar senders.
  • Use spam filters: Enable and update spam filtering options offered by your email provider or messaging platform.
  • Report spam: Help identify malicious bots by reporting spam messages to the platform.

2. Zombie bots

A zombie bot denotes a compromised computer hijacked by a controller, who commands it along with numerous other computers in a botnet. These zombie computers are orchestrated to execute large-scale attacks according to the master botnet owner’s directives. Detecting and eliminating these infections proves challenging, as many owners of infected computers remain unaware of the compromise.


  • Update software: Regularly update your operating system, antivirus, and web browser to patch vulnerabilities.
  • Download cautiously: Download software only from trusted sources and avoid suspicious links or attachments.
  • Strong passwords: Use unique and complex passwords for all accounts. Consider a password manager for better management.

3. Malicious file-sharing bots

Users of peer-to-peer file-sharing services are particularly vulnerable to encountering malicious file-sharing bots. These bots respond to user queries, typically for media files like movies or songs, by claiming to possess the requested file and providing a download link. However, these links are laced with malicious payloads, infecting the user’s computer upon download and execution.


  • Verify sources: Download files from trusted websites and sources you know and recognize.
  • Be cautious of freebies: If a file seems too good to be true (free movie, exclusive song), it probably is.
  • Antivirus software: Use a reputable program to scan downloaded files for hidden malware.

4. Malicious chatterbots

Dating service websites often harbor malicious chatterbots masquerading as genuine human interlocutors. Unwitting users may engage with these bots, unaware that they are malicious programs designed to extract personal information, including credit card details, from unsuspecting victims.


  • Be skeptical: On dating platforms, don’t readily share personal details, especially financial information, with someone you haven’t met.
  • Look for inconsistencies: Be wary of chatbots that dodge questions or struggle with natural conversation.
  • Report suspicious activity: Report any suspicious chatbots to the platform’s administrators.

5. Fraud bots

A plethora of bots fall into the category of fraud. These bots, often resembling scripts, aim to financially benefit their creators through various means, such as generating false clicks for advertisement revenue, creating fake users for sweepstakes entries, or artificially inflating votes for or against a particular cause.


  • Enable two-factor authentication: This adds an extra security layer by requiring a second verification step beyond your password.
  • Review account activity: Regularly monitor your online accounts for suspicious activity and report unauthorized transactions immediately.
  • Be cautious of promotions: Don’t click on links or provide personal information for unsolicited promotions or sweepstakes entries.

6. Scraper Bots

Scraper bots are malicious programs designed to systematically collect data from websites without permission. They act like automated browsers, visiting web pages and extracting information. This information can be anything from product descriptions and pricing to user reviews and even personal details if not properly secured by the website. The motives behind scraper bots can vary. Often, they are used for commercial purposes by competitors trying to gather pricing data or by businesses looking to build targeted marketing campaigns.


  • Implement CAPTCHAs: Websites can use CAPTCHAs (challenge-response tests) to differentiate between human users and bots.
  • Monitor website traffic: Regularly analyze website traffic logs to identify unusual patterns that might indicate scraper bots.
  • Legal measures: If scraping violates your website’s terms of service, consider legal action against persistent offenders.

7. DDoS Bots

DDoS bots, short for Distributed Denial-of-Service bots, are malicious programs designed to overwhelm a website or online service with massive traffic. These bots are typically part of a botnet, a compromised computer network controlled by a single attacker. When activated, the botnet launches a coordinated attack, flooding the target website with requests. This surge in traffic can overload the website’s servers, causing it to crash and become inaccessible to legitimate users.


  • DDoS mitigation services: Security vendors offer services that detect and filter out malicious traffic during attacks.
  • Maintain backups: Regularly back up your website data to minimize downtime if a DDoS attack disrupts service.
  • Have a response plan: Develop a plan to respond to DDoS attacks efficiently, minimizing disruption to legitimate users.

8. Credential Stuffing Bots

Credential stuffing bots are automated programs that attempt to gain unauthorized access to online accounts. These bots use lists of stolen usernames and passwords, often obtained from data breaches. They then try to log in to these accounts on various websites, hoping to find a match. If a user happens to reuse the same username and password combination across multiple websites, a credential-stuffing attack can be successful. This can lead to an account takeover, where the attacker gains access to the victim’s personal information, financial data, or other sensitive details.


  • Enforce strong passwords: Encourage users to create strong, unique passwords and avoid password reuse across different websites.
  • Implement two-factor authentication: Make two-factor authentication mandatory for all accounts or at least for high-risk actions like logging in or making financialtransactions.
  • Monitor login attempts: Track login attempts and implement measures to block suspicious activity, such as after a certain number of failed login tries.

General tips to prevent malicious bots

While combatting malicious bots is challenging, taking preventive measures is crucial. Here are some basic strategies to guard against them:

  • Use reliable antivirus and antispyware programs, keeping them updated automatically.
  • Employ additional opinion scanners to catch any threats your primary antivirus might miss.
  • Exercise caution with unfamiliar or suspicious websites, as they can be sources of bot attacks.
  • Consider installing CAPTCHA scripts on your website to prevent bots from spamming forms.
  • Avoid unauthorized access to your computer through channels like Internet Relay Chats (IRC) and File Transfer Protocols (FTP).
  • Refrain from disclosing personal information during online chats, especially with strangers.
  • Regularly search for copies of your content online to identify potential instances of content scraping.
  • Monitor and remove spam comments from your website, reducing the risk of malware exposure to your readers.
  • Block untrustworthy IP addresses to prevent known bots from accessing your systems.
  • Monitor your site’s speed for any unusual slowdowns, which could indicate bot activity. Implement traffic filtration measures to ensure genuine users, not bots, see your ads.