Monday, 21 April 2014

Search history on windows 8.1 - Part 2

I have recently blogged about windows 8.1 search history and how searched terms/phrases are recorded as LNK files in a post here. But windows also logs searched terms (search history) to the event log and web history (and cache).

From the LNK files, we know the first time a term was searched for, but not the next time or the last time it was searched, which is usually more relevant from an investigation perspective. However, this information can be obtained from the Connected-Search event log file. On disk it would be under:
 \Windows\System32\Winevt\Logs\Microsoft-Windows-Connected-Search%4Operational.evtx

Under Event viewer, you can find it under:
 \Applications and Services Logs\Microsoft\Windows\Connected-Search\Operational

Below is a screenshot for one such log entry.

Searched keyword is 'enscript' and machine was online when search was run

Windows logs all URLs and reference links here. Windows, by default tries to search for everything online as well as on the machine. Even if you are offline, a search URL for online searches is generated and seen here. The screenshot below shows the same search run when machine was offline (not connected to internet).

Searching for 'enscript' when machine is offline

Each time a search is run, an entry is created, sometimes multiple entries (this probably has to do with different views when browsing the search results). For searches (if machine was online), the URL requests and responses are also found in the IE web history and cache database (WebcacheV01.dat). The database is located at
\Users\<USER>\AppData\Local\Microsoft\Windows\WebCache\

The best way to study this data would be by parsing this database either manually (using libesedb and lots of data formatting with additional parsing!) or use a free program like IE10 History reader (or an expensive brand forensic tool). However, if you are just interested in the search terms without dates or other information, a raw search into the datebase files will suffice.

To find searched terms, you will need to search  for URLs beginning with
 https://www.windowssearch.com/search?q=

The screenshot below shows hits when searching the IE web cache files for the above URL using Encase.
Search hits in IE web cache database as seen in encase

Search as you type

An aspect missing from LNK files and the event logs is the search suggestions and interim search results. As Rob Lee hinted to me earlier that a user could search for a term (without hitting Enter or the search button after entering the term in the search box), but not click on any results and none of the above artifacts would be created. Windows uses the 'search as you type' feature and  terms windows guessed for you (as you were typing into the search box) or interim search results are discarded. However you would find some traces of the terms as windows will make online queries for the 'search as you type' feature. If this is not clear, just recall how you search with google. As you begin typing the letters of your keyword into the search box, google automatically suggests most popular searches beginning with those letters. Windows also does the same thing.

Google's search as you type feature

To find such searches which were discarded, search for URLs beginning with
  https://www.windowssearch.com/suggestions?q=

Actually, these are not the suggestions, but the lookups for term/phrase entered into the search box. The data returned (query response) will contain the suggestions.

Below is a screenshot showing the webcacheV01.dat file (and supporting db files) with search hits as displayed in Encase.

Search hits showing Windows querying for popular search term suggestions based on user entered input

Thus there are multiple locations (connected search LNK files, event logs, web cache) where an investigator can find evidence of searches run by a user. Each has its uses and caveats.


Friday, 4 April 2014

Windows 8 Thumbs.db files - still the same and not the same!

Screenshot of folder in Windows 8 showing Thumbs.db

Thumbs.db files have made a comeback in windows 8. Now, like in windows XP, explorer will create these files in every folder containing media files. This used to be a great forensic resource for investigators because thumbnails once created and stored in the Thumbs.db remained there even after the image file itself was deleted. This behavior is also noted with Windows 8.

The only thing that is different is the format of these new Thumbs.db files. It is not the Windows XP format and the usual thumbs.db file viewers including most forensic tools will not parse this file correctly. The format is actually the same as Windows 7 Thumbs.db files. Yes, that was not a typo, I said 'Windows 7'. I had looked into this earlier and the details are available here.

An interesting thing to note is that in windows 8, the same Thumbcache_*.db files are still maintained on a per user basis like windows 7 does. So the Thumbs.db is really a redundant location for these thumbnails as they are already cached in the Thumbcache database. So why the duplication?

Update (Thanks proneer for this tip!):
There are some caveats here. On windows 8, Thumbs.db will only be created in folders under a user profile folder, so anything created in C:\ or C:\program files or C:\program data or any other folder not under a user profile, ie, C:\Users\<USER>\* will not have thumbs.db files. 

But this has got nothing to do with a particular logged in user. A thumbs.db file will be created even when the logged in user browses folders of another user under their profile (as long as file permissions allow that user to write files to the other users' folder).

This behavior is different from Windows 7 thumbs.db where the location does not matter for creation of thumbs.db files.

There is another oddity noted. Sometimes a thumbs.db is created immediately upon folder being opened in explorer, on other occasions it has be triggered by changing the 'view' of the folder to 'Large icons'.

Tuesday, 1 April 2014

Search history on Windows 8 and 8.1

Windows 8 introduced a new feature of saving previously searched terms/keywords. I am refering to the Windows Search functionality which moved from the Start-menu in Windows 7 to the Charms bar in Windows 8.

Search terms are saved on a per user basis. In Windows 8, this is stored as an MRU (Most Recently Used) list in the NTUSER.dat file under the key:
Software\Microsoft\Windows\CurrentVersion\Explorer\SearchHistory\Microsoft.Windows.FileSearchApp

Figure 1 - Search history (MRU) in Windows 8 registry

Windows 8.1

On Windows 8.1 this has changed! These entries are no longer stored in the registry, instead they are stored on disk at:
\Users\<USER>\AppData\Local\Microsoft\Windows\ConnectedSearch\History

They are stored as individual link (LNK) files. Each link file holds a single previously searched for keyword (or phrase).

Figure 2 - Search history in Windows 8.1 stored as LNK files

The format of this link file is similar to the one we are familiar with from earlier versions of windows, however, no dates or other details typically seen in link files are included. All it contains is a link header and a shell item id list. The shell item id list contains the keyword/phrase searched for. Current link file parser scripts/tools will not be able to parse this correctly as they are either not parsing the Shell item id list or not (yet) looking for this specific information. (A shell item id list is seen in many places in the registry, one of the more popular artifacts that uses it is the 'shell bags').

Figure 3 - Search history LNK file showing searched term 'enscript'
As seen in figure 3 above, this link file has the same header as well as basic format. The link guid at offset 0x4 is also the same. Link flags (0x80) indicate only a Shell Item Id List will be present and all other fields are blank (zero). The shell item id list contains a single property identified by guid '{F29F85E0-4FF9-1068-AB91-08002B27B3D9}'. This guid identifies the Microsoft Office Summary Information Properties. Only a single value is populated and that is the keyword/phrase searched for.

Forensic Importance

From a forensic perspective, this ties a search keyword to a user and a date. This means that we now know the date and time when a particular user searched for a specific keyword on the machine. The last modified timestamp gives us the first time that keyword is searched and it does not get updated after, even if the search is repeated. On my machines, all 4 timestamps (created, accessed, modified, entry modified) hold the same value for a single file (see figure 2 above) and don't seem to get updated/altered once created.