Note from Dropbox: The Microsoft firewall client solves the connectivity issues behind an ISA firewall.  Dropbox has tested it for both CNTLM and MS Firewall clients.

Dropbox does not support NTLM authentication and is incompatible with many corporate networks. You can vote for this feature to be added by visiting

Mac users

This article and the instructions provided apply to Win32 environments (Windows XP, Vista, etc.). Mac users should check Authoxy following the instructions provided with the installer.

Win32 users

Following the directions below may upset your network administrator. This has only been tested with ISA server 2004 with * whitelisted.

Download Cntlm

Install Cntlm

Unzip the contents of the download and run setup.bat

Configure Cntlm

  1. Navigate to C:\Program Files\Cntlm
  2. Open cntlm.ini in notepad
  3. Change the following:
    • Username Your_Username
    • Domain Your_Domain
    • Password Your_Password
    • Proxy Your_Proxy’s_IP:Port (probably 8080)
  4. Place a # infront of the second proxy.
  5. Save cntlm.ini

Go to services and start the Cntlm service

Set Auth and get password hash

Open up CMD and navigate to the Cntlm folder

CD C:\Program Files\Cntlm


cntlm -M

If that does not work try

cntlm -M

You should see an output like this:

[ Profile 0 ]
Auth NTLMv2
PassNTLMv2 72F78A2B364583291090E919B5CE9E04

Auth NTLMv2 <– Replace the whole #Auth line in cntlm.ini with this PassNTLMv2 72F78A2B364583291090E919B5CE9E04 <– Replace the whole password line in cntlm.ini with this Save cntlm.ini Restart the cntlm service.

Configure Dropbox

Open dropbox preferences Choose network tab Select Manually enter proxy settings Server Port 3128 Hit OK.

Additional Notes

  • Instructions seem to work up to the part that says “Run cntlm with the -M flag to find your settings”. cntlm does not have a -M flag. Also, ccntlm.ini does not have an Auth line!
  • Cntlm does have an -M flag, make sure you use -M not -m.
  • cntlm.ini does have an auth line look for the line #Auth LM
  •  If the cntlm service starts but stops immediately, try rebooting the computer.
  • If the cntlm service starts but stops immediately, make sure you installed cntlm to the default path (%PROGRAMFILES%\Cntlm). The service apparently searches for cntlm.ini in this directory. If you used a different path you can move cntlm.ini to the default path (usually c:\Program Files\cntlm\).
  • Proxy type should be (or remain) HTTP