What Are Probing Bots?
Probing bots are automated programs designed to scan and identify vulnerabilities in websites and online services. These bots systematically search for weaknesses in security systems, looking for open ports, misconfigured settings, outdated software, or other exploitable elements.
While probing bots can be used for legitimate purposes, such as security testing or web indexing, they are more often associated with malicious intent, such as launching attacks, harvesting data without permission, or testing defences before a more significant cyberattack.
How Do Probing Bots Work?
Attackers use probing bots to gather intelligence on potential targets, often before launching a full-scale attack.
Probing bots work by systematically scanning websites and applications for vulnerabilities, hidden pages, or sensitive information. Here’s how they typically operate:
URL Enumeration: Probing bots attempt to access a wide range of URLs, including common paths like /admin, /login, or /config. They may also try variations and combinations to discover hidden or unprotected pages.
Parameter Tampering: Bots often modify URL parameters to test how the application handles unexpected inputs. This can include adding special characters, manipulating query strings, or injecting malicious code to find exploitable weaknesses.
Form and Input Scanning: Probing bots may interact with forms and other input fields, submitting various types of data to see how the site processes and validates input. This helps them identify vulnerabilities like SQL injection or cross-site scripting (XSS).
404 Error Monitoring: Bots use 404 errors as feedback. When they attempt to access non-existent pages, they record which paths result in errors, and which don’t. This information helps them refine their scanning strategy to focus on areas that might yield results.
Session and Cookie Testing: Some probing bots attempt to manipulate session IDs or cookies to gain unauthorized access to restricted areas of the site. They may also test session management for weaknesses, such as session fixation or hijacking.
Rate of Requests: Probing bots typically generate requests at a much higher rate than a human user would, often targeting multiple endpoints simultaneously. This high frequency of requests helps them quickly cover a large portion of the site’s surface.
Response Analysis: After making requests, probing bots analyze the responses they receive. They look for specific error messages, response codes, or content that might indicate the presence of vulnerabilities or misconfigurations.
Impact of Probing Bots on Application Security
Probing bots represent a significant risk to organizations by exposing them to potential cyberattacks.
Vulnerability Exposure: Probing bots can expose security flaws, leading to potential exploitation by attackers.
Data Breaches: They can locate and access sensitive information, increasing the risk of data breaches.
Resource Drain: Constant probing can strain server resources, slowing down legitimate traffic and increasing operational costs.
Precursor to Attacks: Probing often serves as a reconnaissance step before more significant attacks such as DDoS, SQL injection, malware and more.
Detection Challenges: Differentiating between legitimate bots (like search engines) and malicious probing bots can be difficult, complicating defence strategies.
Why Traditional Methods Fail to Detect Probing Bots?
Detecting probing bots is inherently difficult due to several advanced tactics they employ to evade detection:
Mimicking Legitimate Traffic: Probing bots often replicate the behaviour of regular users or well-known bots, like search engine crawlers. They simulate human-like browsing activities such as clicking links, scrolling, or spending varied amounts of time on pages—to blend in with normal traffic patterns. This makes it challenging to distinguish them from genuine users using simple rule-based detection.
Advanced Evasion Techniques: Probing bots utilize various techniques to avoid detection by security systems:
IP Rotation: Frequently changing IP addresses to avoid being blacklisted.
User-Agent Spoofing: Changing user-agent strings to mimic popular browsers or legitimate bots, making it hard for systems to filter them based on agent identification.
Distributed Probing: Spreading their activities across multiple IP addresses and geographical locations to distribute their footprint and avoid triggering rate limits or detection thresholds.
Low and Slow Attacks: Some probing bots employ “low and slow” techniques, where they perform their activities at a very slow pace to stay under the radar. These bots make fewer requests over a long period, reducing the chances of detection by rate-limiting mechanisms or anomaly detection systems designed to spot rapid or high-volume requests.
Find out how AppTrana’s custom rules blocked a low and slow DDoS attack in our case study here.
Targeted and Context-Aware Probing: Probing bots can be highly targeted, focusing on specific applications, forms, or endpoints. They might probe areas of a website that are less monitored or that provide valuable information about the infrastructure or exposed services. They can also adapt their probing strategies based on the responses they receive, learning from any defences they encounter.
What are the Signs of Probing Bots?
Repeated Access to Non-Public URIs: Repeated attempts to access hidden directories, admin panels, or non-public resources (e.g., /admin, /login, /backup) suggest a bot probing for vulnerabilities.
High Frequency of 404 Errors: If you observe a high number of 404 errors from the same IP address within a short period, it could indicate that a bot is systematically scanning for non-existent pages.
Frequent IP Changes: A pattern of rapid IP changes or multiple requests coming from different IPs within the same range or from various locations can be a sign of bot activity using IP rotation or proxy networks.
Unusual User-Agent Strings: Requests with outdated, malformed, or unusual user-agent strings that don’t match typical user traffic can indicate probing bots. Some bots may also spoof user-agent strings to appear as legitimate browsers or known services.
Consistent Query Patterns: Repeated queries or scans that follow a predictable pattern, such as sequentially checking every URL path or parameter, suggest automated probing rather than human browsing behaviour.
Access to Vulnerability-Prone Endpoints: Frequent requests to URLs associated with common exploits (e.g., /phpinfo.php, /etc/passwd) or database endpoints (/wp-admin, /admin.php) can be signs of probing bots scanning for vulnerabilities.
High Rate of Request to Sensitive Operations: Unusually high requests for sensitive operations (e.g., login attempts, password resets, or API endpoints) without typical user behaviour (like viewing pages or products) suggest probing attempts.
Repeated Rate Limiting or Blocking: Multiple instances where IPs hit rate-limiting thresholds or are temporarily blocked and then return with new IPs may indicate bot traffic trying to evade defences.
How AppTrana WAAP Stops Probing Bots?
AppTrana WAAP’s bot protection module effectively blocks bots using advanced behavioral analysis and machine learning. It also offers customizable bot policies to ensure accurate detection with minimal false positives. It continuously monitors traffic to establish normal user behavior and detect deviations such as rapid, automated requests or unusual access patterns.
AppTrana’s ML based behavioral analysis distinguishes malicious bots from legitimate users, even when bots mimic human behavior, allowing it to identify sophisticated threats that traditional methods might miss.
AppTrana also provides user-defined bot policies for more precise control. With self-service rules, you can adjust mitigation methods based on specific user activity in your applications. For example, by choosing the “Activity Log Only” option for 404 errors, attempts to access non-existent pages will be logged rather than instantly blocked. This allows you to monitor suspicious behavior before deciding on further action.
Alternatively, you can configure a self-service rule to increase the bot score for each 404 error. This higher score makes the visitor appear more suspicious, which helps escalate the bot’s score faster and improves threat detection.
For a more proactive approach, the “Block” option will block a visitor as soon as they reach the offense limit for 404 errors, effectively stopping probing bots promptly.
