Bot Threats
September 14, 2023

OpenBullet Bot Threat

OpenBullet is a powerful and infamous open-source software used by cybercriminals to automate attacks on websites. OpenBullet gained notoriety for its efficiency in carrying out credential stuffing attacks, where attackers use a large number of stolen usernames and passwords to gain unauthorized access to user accounts on various websites.

The new version OpenBullet 2 has been designed as cross platform automation suite of tools, based on a .NET core. It’s particularly strong at custom data scraping, and can be used for many legitimate purposes including pen-testing, and writing automated test scripts.

OpenBullet's popularity lies in its ability to easily adapt to different websites and services. It’s Open Source, and has a community available for help and discussions. With its user-friendly interface and .NET core, users can create custom configurations tailored to their specific needs. This means potential attackers can specifically target their victims websites with a custom attack based on its vulnerabilities.

We aim to provide valuable insights into the modus operandi of attackers and how OpenBullet and automation tools can play a central role in executing these malicious activities. Understanding these tactics will empower website owners and administrators to fortify their defences and safeguard their online assets against the specific threat from OpenBullet and other automated web platforms.

Understanding the Landscape of Website Attacks

The digital landscape is fraught with various threats, and website attacks are among the most prevalent and damaging. Attackers target websites for various reasons, ranging from data theft and financial gain to political motives and reputational damage. Common attack vectors include Account Take Over (ATO) based on credential stuffing, IP theft from data scraping, SQL injection, cross-site scripting (XSS), and Distributed Denial of Service (DDoS) attacks.

Analyzing OpenBullet's Attack Methodology

  1. Configurations and Target List: Attackers using OpenBullet begin by creating configurations that define the parameters of the attack, such as the target website's URL and the login credentials list. These configurations are then shared on underground forums and marketplaces, making them easily accessible to others. Custom targeted attacks on a website can then be easily made by using OpenBullet, which are much more dangerous and harder to detect than generic scripts.
  2. Credential Stuffing Attacks: Armed with the configurations, attackers launch credential stuffing attacks. OpenBullet automates the process of trying multiple username-password combinations at a rapid pace, exploiting the fact that many users reuse passwords across different platforms. As a result, even a single successful login can lead to a cascade of compromises.
  3. CAPTCHA Solving: To bypass CAPTCHA challenges, OpenBullet incorporates CAPTCHA-solving services. This enables attackers to automate the process of solving CAPTCHAs, further streamlining the attack and increasing its success rate. Many OpenBullet users also use Capsolver - which has integrations to solve most CAPTCHAs as a paid service-
  4. Proxies and Anonymity: OpenBullet allows attackers to employ proxies, facilitating anonymity and evading IP-based rate limits and bans imposed by the target website's security systems. These can use millions of domestic IPs and hide their digital provenance from detection.

The Impact of OpenBullet Attacks

The impact of OpenBullet attacks is far-reaching, affecting both website owners and their users. Some of the consequences include:

  • Financial Loss: Successful attacks may lead to financial losses due to unauthorized access to user accounts, fraudulent transactions, or theft of sensitive information like credit card details.
  • Reputation Damage: Websites that fall victim to OpenBullet attacks often experience a severe blow to their reputation, leading to loss of trust among users and partners.
  • Legal and Regulatory Consequences: Data breaches resulting from OpenBullet attacks can attract legal actions and penalties due to non-compliance with data protection regulations.

Strengthening Your Website's Defences

To mitigate the risks associated with OpenBullet attacks and bolster your website's security with a dedicated security platform for detecting and blocking the bots at the network edge.

VerifiedVisitors detects automated traffic at the edge of the network, before in can cause hard. Our hybrid cloud infrastructure allows you to provide zero trust in the Cloud - protecting all your endpoints, websites, API and mobile.

Traditional defences against OpenBullet don’t work.

IP Rate Limiting: Enforcing IP rate limiting to detect and block suspicious activities from specific IP addresses, might slightly mitigate the impact of credential stuffing attacks by reducing the volume of attacks, but doesn’t solve the problem. All you are achieving is making the service slow for your legitimate users, by punishing them for the actions of the few. Although rate limiting can be a good emergency measure just to keep services running, it’s at best a band-aid.

Adding CAPTCHA: We’ve seen how OpenBullet works with partners and other frameworks to pass CAPTCHA.

Multi-Factor Authentication (MFA): Implementing MFA clearly works to reduce account attacks. However it does means you will inevitably see large decreases in user logins. MFA is a real barrier to custom adoption and utilisation. Again, punishing all legitimate and verified visitors by enforcing a rigid MFA for each login isn’t the answer, unless the user base buys strongly into the need for MFA, for financial services, banking and other vertical applications. Adopting strict MFA for all users is time consuming, and relies on end-user adoption, training and the customer willingness to use 2FA services.


In conclusion, targeted website attacks orchestrated with the help of OpenBullet and other such dedicated automation tools, pose significant risks to online businesses.

By understanding the tactics used by attackers and taking proactive measures to fortify website defences in the cloud, we can minimize the impact of such attacks and safeguard our digital assets, without affecting our users. The popularity of OpenBullet is a potent reminder that security must remain a top priority in the ever-evolving landscape of cybersecurity.

Photo by Velizar Ivanov on Unsplash

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