"Give me six lines written by the most honourable of men and I will find in them an excuse to hang him," as Cardinal Richelieu may have said.

In six paragraphs, Bill Brown betrays a lack of understanding about modern mass surveillance methods and the risks posed in this digital age (Letters, June 17).

Maintaining mass surveillance does not require numbers of staff beyond the means of Government agencies. Notwithstanding that GCHQ and MI5 employ one person for every 6000 adults in the UK, while making extensive use of additional consultants, interception of digital communications needs not be a labour intensive operation. Automated systems can hoover up data for bulk analysis by computers without bureaucrats monitoring all of the information in real time. That such surveillance may produce inaccurate intelligence is not necessarily a barrier in Whitehall, where the ineffectiveness of big Government IT projects is rarely a major barrier to misconceived implementation.

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It may be a comfort to believe that one has nothing to hide or fear but this is a false security. One can never know what false conclusions may be inferred from information about our communications, with adverse consequences when the shadow of suspicion is cast; but even true deductions can be harmful to innocent individuals, revealing health conditions, intimate relationships or a host of other details of our lives that individuals quite rightly wish to keep private. People should be free to seek information about medical conditions (physical or mental), domestic abuse or sexuality, approach rape crisis centres and seek marital advice without fear that civil servants have access to all the intimate details of our lives.

Details now emerging about how UK officials spied on foreign delegates' phone and internet use at the 2009 London G8 summit amply demonstrate how surveillance is used to advance Government policy objectives. For political activists, whistleblowers corresponding with journalists, or anyone who might ever be an irritation to current or future governments, there is everything to fear from a permanent record of our communications.

Dr Geraint Bevan,

NO2ID Scotland,

3e Grovepark Gardens,

Glasgow.

RAF Menwith Hill is a communications spy centre in England and it can be seen on aerial maps. What is open to debate is what function it actually serves. It is an open secret that, from as far back as 1954, the US has been monitoring communications from this base allegedly as part of project Echelon, which originally had the remit of spying on the USSR during the Cold War as part of a global surveillance project involving the US, UK, Canada, Australia and New Zealand.

The practical spin-off of this shared project was that it allowed national security agencies to circumvent regulations preventing security services from spying on their own citizens without formal judicial agreement in individual cases. Effectively: "You spy on us, we spy on you then share the good bits and nobody need know a thing about it."

More than half of almost 2000 employees at the facility, which monitors all electronic signals passing through or accessible from the UK, are members of the US security services. That fact alone should be a matter of concern; just what are they doing and why are they doing it here?

Since the hardware at Menwith Hill is continuously updated to keep pace with the rapid pace of change in the communications field, to suggest that internet traffic is not routinely monitored stretches credulity to breaking point.

Those who believe the scale of the operation renders mass surveillance impossible should pause and consider the "targeted" adverts routinely displayed on their social media pages. Now how do you think that works?

David J Crawford,

131 Shuna Street, Glasgow.

It is sometimes said that even if the state has access to all our emails, website visits and use of social websites, the intelligence services do not have the manpower to analyse their contents. I believe Google "reads" all my emails and supplies the appropriate words to advertisers.

A typical example is a recent email I received about a friend planning a trip to Iceland, alongside which were adverts for guided tours in Iceland. In America the US Patriot Act and Foreign Intelligence Surveillance Act allow the law enforcement authorities to access personal data in cloud storage facilities. Data stored by American companies such as Apple, Google, Microsoft and Amazon is also legally accessible to US authorities.

In large databases, errors are inevitable, particularly when you cannot check the accuracy of the data about yourself. It is not difficult to imagine how supposedly confidential data can be misused by individuals, companies and the state, even if you hold the naive view that "if you have nothing to hide you have nothing to fear".

People who have had banking information misused by criminals or been denied credit because of errors in the database have found out the hard way that they did indeed have much to fear. The result of errors could be more serious, for example being refused a visa to enter a country.

The state and commercial companies already hold a great deal of personal data on us all. We should make every effort to ensure the information about ourselves is available for us to correct and we retain some control and knowledge of its use.

Hugh Boyd,

65 Antonine Road,

Bearsden.

I am saddened by the ease with which Bill Brown gives up his personal privacy (Letters, June 17). Over centuries people have fought and died to preserve our liberty not only from external foes like Germany but also our own monarch and Government.

It goes back to English legal doctrine. Sir Edward Coke, in the Semayne's case in 1604, argued: "The house of every one is to him as his castle and fortress, as well for his defence against injury and violence as for his repose."

The deeply naive statement: "If you have done nothing wrong you have nothing to fear" merely exposes the individual to the situation where someone else decides what is right and what is wrong. Many perfectly legal pursuits have been made illegal over the years by Parliament for reasons which were justified by national security or public safety.

If anyone really believes Government agencies do not have the resources to accumulate and handle vast amount of personal information, look at the budgets apportioned to national security projects. If they run short of cash do you really believe they would not sell your information to commercial interests? Just look at what happens to the information DVLA hold on you. How much would an insurance company pay to know you had been researching genetic diseases on Google? Search engines are there to refine data after all.

If you do not value your privacy no-one will respect it.

David Stubley,

22 Templeton Crescent,

Prestwick.