Dead Letter Drops and Geo Caches

For Whistleblowers, unlike a Spy or Secret Agent, the use of Dead Drops / Dead Letter Drops or Caches, is unlikely to be a regular occurrence, and may only need to be used once, in order to pass on some actual physical evidence which supports a whistlelblower's claims.

However, pretty much the same precautions apply, both in choosing an appropriate location for the drop, signaling when and where there is something to be picked up, and taking anti-forensic precautions, in case the physical package is lost or intercepted, whilst preserving it from damage by the weather or even by wild animals etc.

You may be able to disguise your real "whistleblower" Dead Drop activity if it is near an "innocent" GeoCache site.

  1. Wikipedia article on Dead Drops / Dead Letter Drops etc.

  2. Wikipedia article on Geo Caching

  3. Magnetic Geo Cache tips


    With a magnetic nano cache you can really have some fun when deciding on where to put it. It obviously needs something ferrous to stick to and because of its magnet, you can put it in places where regular cache container wouldn't be suitable.

    Try placing the cache underneath something such as a park bench or bridge support. You can be as devious as you want - placing it under the bottom step on a metal stairway means that no-one will be able to see it unless they get down on their hands and knees to do so.

    Nano caches are ideally suited for built up areas or urban-caching where you can find more places to site the magentic cache than in the countryside.

    Here are some ideas for you:

    * Under a park bench.
    * Under some steps.
    * Under a bridge.
    * Attach it to some railings.
    * On a fence post.

    Remember that just because it's magnetic doesn't mean you can't put it a hidey hole somewhere.

    Make sure that you don't place it where workmen will find it. Trust me if a BT engineer comes to look into one of their boxes he will immediately spot anything out of place on it and you risk losing the cache. The cache should be placed out of the way.

Anti-forensic precautions

As with Postal or Courier sent messages, you might also need to take precautions against leaving characteristic DNA, fingerprint, fibre , particle etc. on the Container or the actual message itself.

Caches or Dead Drops outside, exposed to the weather, will probably involve metal or plastic etc. waterproofing, which usually retains fingerprints and DNA samples etc. quite well.

Anything sticky e.g. tape or adhesive used to weatherproof or attach the container to something, could also trap fibres, dust particles, hair, skin cells etc.

Signals about Caches or Dead Drops

See the section on Covert Channel Signals for Meetings or Dead Letter Drops for some ideas about Covert Channel Signals,

There may need to be different signals to signal that there is something at the Dead Drop to be picked up, that the Dead Drop is suspected of being under surveillance, and that an alternative Dead Drop should be used instead, or that an urgent Physical Meeting is needed..

In spy fiction and in real life espionage cases, such signals usually involve something inconspicuous, which the other person can notice without stopping and reading a note e.g. a window with curtains, a venetian blind or a light switched on or off, a chalk mark, or thumb tack on the pavement or on a bit of street furniture like a litter bin or telegraph pole etc.

The internet provides a lot of alternative methods of sending or receiving a Covert Channel signal.

About this blog

We know that there are decent, honest, trustworthy individual politicians, civil servants, law enforcement, intelligence agency personnel and broadcast, print and internet journalists etc., who often feel powerless or trapped in the system. They need the assistance of external, detailed, informed, public scrutiny to help them to resist deliberate or unthinking policies, which erode our freedoms and liberties.

Some of these people will, in the public interest, act as whistleblowers, and may try to leak documents or information to the mainstream media, or to political blog websites etc.

Here are some Spy Blog "Hints and Tips", giving some basic preecautions, and some more obscure technical tips, which both whistleblowers, journalists, and bloggers need to be aware of, in order to help preserve the anonymity of whisteleblowing or other journalistic sources, especially in the United Kingdom, but applicable in other countries as well.

Whistleblower anonymity may not always be possible, or even necessary, forever into the future, but it is usuially crucial during at least the early stages of a "leak", whilst it is being evaluated by others, to see if it merits wider publication and publicity.

Email & PGP Contact

Please feel free to email your views about this blog, or news about the issues it tries to comment on.


Our PGP public encryption key is available for those correspondents who wish to send us news or information in confidence, and also for those of you who value your privacy, even if you have got nothing to hide.

You can download a free copy of the PGP encryption software from
(available for most of the common computer operating systems, and also in various Open Source versions like GPG).

We look forward to the day when UK Government Legislation, Press Releases and Emails etc. are Digitally Signed so that we can be assured that they are not fakes. Trusting that the digitally signed content makes any sense, is another matter entirely.


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CryptoParty London

CryptoParty London

Most months there is a CryptoParty London event. where some of these Hints and Tips and other techniques are demonstrated and taught.

Usually at:

Juju's Bar and Stage 15 Hanbury St, E1 6QR, London

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