Banner Grabbing

Banner grabbing is a method used by attackers and security teams to obtain information about network computer systems and services running on open ports. A banner is a text displayed by a host that provides details such as the type and version of software running on the system or server.The screen shows the network server’s software version number and other system data, providing cybercriminals an edge during cyberattacks. Banner snatching is the practice of gathering program banner data, such as the name and version. Hackers can manually or automatically collect the banners using the OSINT program. One of the crucial steps in both offensive and defensive penetration testing scenarios is banner capture.

Types of Banner Grabbing:

  1. Active Banner Grabbing: In this method, Hackers send packets to a remote server and analyze the response data. The attack involves opening a TCP or similar connection between the origin and the remote server. An Intrusion Detection System (IDS) can easily detect an active banner.
  2. Passive Banner Capture: This method allows hackers and security analysts to get the same information while avoiding disclosing the original connection. In passive banner grabbing, the attackers deploy software and malware as a gateway to prevent direct connection when collecting data from the target. This technique uses third-party network tools and services to capture and analyze packets to identify the software and version being used. run on the server.  

Usage:

Hackers can perform a banner-grabbing attack against various protocols to discover insecure and vulnerable applications and exploits. You can use banner grabbing to gather data from a wide range of services, protocols, and banner kinds. For the discovery process, a variety of techniques and instruments might be developed. In general, banner grab enables an attacker to identify the operating system, network servers, and services that are running along with their instances on open ports. A hacker, or pen tester, can easily search for known and exploitable vulnerabilities in a version of an application given the type and version information.

Service Ports:

  • Port 80 is running on Hypertext Transfer Protocol (HTTP) service. 
  • Port 21 is running on the File Transfer Protocol (FTP) service.
  • Port 25 runs on the Simple Mail Transfer Protocol (SMTP) service. 

Commonly Used Banner Grabbing Tools

Both good and bad guys use these tools for banner grabbing:

  • Telnet : Telnet is a classic cross-platform client that lets users interact with remote services for banner grabbing. Telnet users typically use port scanners first to identify open ports on the target organization’s remote server.
  • Wget : Wget also lets users get banner information from any remote or local HyperText Transfer Protocol (HTTP) or File Transfer Protocol (FTP) server. An HTTP server, also known as a “web server,” answers HTTP requests, as when you type a website link on your browser to open the page you are looking for. An FTP server, meanwhile, facilitates file transfers done over the Internet. Companies typically use FTP servers to upload and download large files that users cannot send via email.

Important Points:

  • Banner Grabbing is used in Ethical Hacking to gather information about a target system before launching an attack.
  • In order to gather this information, the Hacker must choose a website that displays banners from affiliate sites and navigate from the banner to the site served by the affiliate website.
  • Banner Grabbing can be done through manual means or through the use of automated tools such as web crawlers, which search websites and download everything on them, including banners and files. 

Countermeasures:

  • To avoid banner-grabbing attacks, companies can disable their banners on shady affiliate websites that are associated with known hacker forums where malicious tools are sold.
  • Companies can also pay a fee to legitimate websites for their affiliate program to ensure that reputable and established sites will display the banners of the company in an attempt to target legitimate customers who would be interested in purchasing their product or service.
  • Companies should always patch any software that they use, including antivirus programs and operating systems.

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