Unblocking a DLL on a company machine. How?

The file contains an alternate data stream that indicates that the content was retrieved from the Internet and is not secure. This is a feature of the NTFS file system, one that's unfortunately well hidden because Explorer has no support for showing their content. You can see them from the command prompt with the DIR /R command option. And type their content with TYPE filename:streamname. And delete them with DELETE filename:streamname

Other tricks is to copy the file to a file system that doesn't support alternate data streams, that slices them off the file. A flash drive for example. Or a zip utility.

Later versions of Windows, I think starting with Win7, has built-in support for this in Explorer. Right-click the file, Properties and click "Unblock".

SysInternals has a great command line utility called Streams. This proved very useful for me.

Streams v1.56 - Enumerate alternate NTFS data streams Copyright (C) 1999-2007 Mark Russinovich Sysinternals - www.sysinternals.com

usage: streams [-s] [-d] <file or directory>
-s Recurse subdirectories
-d Delete streams

Execute the following command in the directory you wish to remove streams from (same effect as copying to USB/FAT32 drive)

streams.exe -d -s *.*

Unblock the zip file first, and then extract the dll's. Actually that's what they instruct to do here.

Only for general understanding. NTFS supports streams (see http://msdn.microsoft.com/en-us/library/aa364404%28VS.85%29.aspx). The full name of a stream is filename:stream_name:stream_type. So one can easy write some additional information about a file in an additional stream of file. If you download a file from the internet Internet Explorer write some simple information in a stream with the name Zone.Identifier. If you have a file test.dll downloaded from the internet you can use

more < test.dll:Zone.Identifier

to see information from the stream. You will see something like

[ZoneTransfer]
ZoneId=3

Unblocking is not much more as deleting of this stream. I recommend you to read http://weblogs.asp.net/dixin/archive/2009/03/14/understanding-the-internet-file-blocking-and-unblocking.aspx for more detaild information