MI5's recently appointed boss has placed the ability to intercept communications at the centre of the security agency's counter-terrorism efforts.

Andrew Parker's most detailed justification of the controversial surveillance programmes by GCHQ and the NSA, came in a pre-planned speech (transcript here) to the Royal United Services Institute at Thames House in London on Thursday. The second published speech from Parker, director general of the security service, only made passing reference to this week's shocking terrorist attack on the ‪Charlie Hebdo offices in Paris.‬

"It is too early for us to come to judgments about the precise details or origin of the attack but it is a terrible reminder of the intentions of those who wish us harm," Parker said. "As you would expect, we are offering our French colleagues our full support as they respond."

The speech instead focused on the challenge posed by Islamist inspired terrorism and the "critical challenge" posed by technological change.

Isis and Irish republicans among 'top' threats

One of the main threats comes from around 600 extremists are among the many Britons who have travelled to Syria, many of whom have joined ISIS (IS), but that's not the only threat which dangers posed by other Jihadists and dissident Irish republicans, among others.

"Access [to] terrorist communications is vital to MI5’s ability to keep the country safe," Parker argued. The MI5 boss went on to argue that monitoring terrorist communications had become more difficult because of the Snowden revelations (something he has covered before) before outlining specific incidents where tapping communications has led to foiling terrorist plots.

Changes in the technology that people are using to communicate are making it harder for the Agencies to maintain the capability to intercept the communications of terrorists. Wherever we lose visibility of what they are saying to each other, so our ability to understand and mitigate the threat that they pose is reduced. The value that visibility of online communications can bring to understanding terrorist threats is clear. Just a few weeks ago it was revealed in court that the first person in the UK to be convicted of terrorist offences in connection with the Syria conflict had received advice on how to access extremist training and weaponry in Syria through online contact with other extremists based overseas. And this is not an isolated incident. Almost all of MI5’s top priority UK counter terror investigations have used intercept capabilities in some form to identify, understand or disrupt plots seeking to harm the UK and its citizens. The further reduction of this capability will seriously harm our ability to investigate and disrupt such threats in the future. For the evidence, look back over recent years. Consider the case of the largest and most serious terrorist plot that we have ever faced – Operation OVERT. Between 2008 and 2010 ten individuals were convicted of plotting to blow up multiple transatlantic airliners. The investigation employed a range of intelligence and evidence gathering techniques in order to understand the risks posed by the conspirators. A key part of the evidence which brought the plotters to justice was coded conversations by email, forensically retrieved by police following their arrest, between the conspirators and Al Qaeda linked extremists in Pakistan, in which they discussed the preparations for their attacks and the selection of targets. Or consider the 2012 conviction of nine individuals for planning to attack the London Stock Exchange and other iconic targets in the capital. Information recovered forensically following the group’s arrest indicated that electronic communications over the internet played a key role in how the group met and stayed in touch, including through internet forums and other publicly available communications methods.

Dark web another area of interest

Terrorists use the internet to "spread propaganda, to radicalise impressionable individuals, to arrange travel, to move money" as well as for planning and organising more generally, according to Parker, who went on to repeat previous warnings that terrorist communications were "going dark".

That is why the capability to intercept these communications is so important to MI5 – the ability to monitor the terrorists’ communications as they plan is central to our chances of knowing their intentions and stopping them. So, if we lose that ability, if parts of the radar go dark and terrorists are confident that they are beyond the reach of MI5 and GCHQ, acting with proper legal warrant, then our ability to keep the country safe is also reduced.

The Intelligence and Security Committee of Parliament has been considering the issues of Privacy and Security since the summer of 2013. "Senior intelligence professionals should contribute to the debate and help ensure that in so far as possible it is grounded in a proper knowledge of the facts and the consequences of different options," according to Parker, who added that we need a "mature debate about privacy in the digital age".

I’ve said before and I’ll say again MI5 does not browse through the private lives of the population at large. We need to have powerful capabilities that enable us to range widely, with the potential to reach anyone who might threaten national security – but with our efforts always concentrated on the tiniest minority who actually present threats. We all value our privacy – and none of us want it intruded upon improperly or unnecessarily. But I don’t want a situation where that privacy is so absolute and sacrosanct that terrorists and others who mean us harm can confidently operate from behind those walls without fear of detection.