How Reverse-Connecting Trojans Work

Reverse-connecting Trojans let an attacker access a machine on the internal network from the outside. The hacker can install a simple Trojan program on a system on the internal network, such as the reverse WWW shell server. On a regular basis (usually every 60 seconds), the internal server tries to access the external master system to pick up commands. If the attacker has typed something into the master system, this command is retrieved and executed on the internal system. The reverse WWW shell server uses standard HTTP. It's dangerous because it's difficult to detect: it looks like a client is browsing the Web from the internal network.

---

Hacking Tools

TROJ_QAZ is a Trojan that renames the application notepad.exe file to note.com and then copies itself as notepad.exe to the Windows folder. This will cause the Trojan to be launched every time a user runs Notepad. It has a backdoor that a remote user or hacker can use to connect to and control the computer using port 7597. TROJ_QAZ also infects the Registry so that it is loaded every time Windows is started.

Tini is a small and simple backdoor Trojan for Windows operating systems. It listens on port 7777 and gives a hacker a remote command prompt on the target system. To connect to a Tini server, the hacker telnets to port 7777.

Donald Dick is a backdoor Trojan for Windows OSs that allows a hacker full access to a system over the Internet. The hacker can read, write, delete, or run any program on the system. Donald Dick also includes a keylogger and a Registry parser, and can perform functions such as opening or closing the CD-ROM tray. The attacker uses the client to send commands to the victim listening on a predefined port. Donald Dick uses default port 23476 or 23477.

NetBus is a Windows GUI Trojan program and is similar in functionality to Donald Dick. It adds the Registry key HKEY_CURRENT_USER\NetBus Server and modifies the HKEY_CURRENT_USER\NetBus Server\General\TCPPort key. If NetBus is configured to start automatically, it adds a Registry entry called NetBus Server Pro in HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices.

SubSeven is a Trojan that can be configured to notify a hacker when the infected computer connects to the Internet and can tell the hacker information about the system. This notification can be done over an IRC network, by ICQ, or by email. SubSeven can cause a system to slow down, and generates error messages on the infected system.

Back Orifice 2000 is a remote administration tool that an attacker can use to control a system across a TCP/IP connection using a GUI interface. Back Orifice doesn't appear in the task list or list of processes, and it copies itself into the Registry to run every time the computer is started. The filename that it runs is configurable before it's installed. Back Orifice modifies the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices Registry key. BackOrifice plug-ins add features to the BackOrifice program. Plug-ins include cryptographically strong Triple DES encryption, a remote desktop with optional mouse and keyboard control, drag-and-drop encrypted file transfers, Explorer-like file system browsing, graphical remote Registry editing, reliable UDP and ICMP communications protocols, and stealth capabilities that are achieved by using ICMP instead of TCP and UDP.

BoSniffer appears to be a fix for Back Orifice but is actually a Back Orifice server with the SpeakEasy plug-in installed. If BoSniffer.exe, the BoSniffer executable, is run on a target system, it attempts to log on to a predetermined IRC server on channel #BO_OWNED with a random username. It then proceeds to announce its IP address and a custom message every few minutes so that the hacker community can use this system as a zombie for future attacks.

ComputerSpy Key Logger is a program that a hacker can use to record computer activities on a computer, such as websites visited; logins and passwords for ICQ, MSN, AOL, AIM, and Yahoo! Messenger or webmail; current applications that are running or executed; Internet chats; and email. The program can even take snapshots of the entire Windows desktop at set intervals.

Beast is a Trojan that runs in the memory allocated for the WinLogon.exe service. Once installed, the program inserts itself into Windows Explorer or Internet Explorer. One of Beast's most distinct features is that it's an all-in-one Trojan, meaning the client, the server, and the server editor are stored in the same application.

CyberSpy is a telnet Trojan that copies itself into the Windows system directory and registers itself in the system Registry so that it starts each time an infected system is rebooted. Once this is done, it sends a notice via email or ICQ and then begins to listen to a previously specified TCP/IP port.

Subroot is a remote administration Trojan that a hacker can use to connect to a victim system on TCP port 1700.

LetMeRule! is a remote access Trojan that can be configured to listen on any port on a target system. It includes a command prompt that an attacker uses to control the target system. It can delete all files in a specific director, execute files at the remote host, or view and modify the Registry.

Firekiller 2000 disables antivirus programs and software firewalls. For instance, if Norton AntiVirus is in auto scan mode in the Taskbar, and AtGuard Firewall is activated, the program stops both on execution and makes the installations of both unusable on the hard drive. They must then be reinstalled to restore their functionality. Firekiller 2000 works with all major protection software, including AtGuard, Norton AntiVirus, and McAfee Antivirus.

The Hard Drive Killer Pro programs offer the ability to fully and permanently destroy all data on any given DOS or Windows system. The program, once executed, deletes files and infects and reboots the system within a few seconds. After rebooting, all hard drives attached to the system are formatted in an unrecoverable manner within only one to two seconds, regardless of the size of the hard drive.