Controversial powers used by spy agencies to hoover up large volumes of data play an important role in fighting terrorism and serious crime, a major review has concluded.
So-called bulk capabilities deployed by MI5, MI6 and GCHQ have a "clear operational purpose", the official terror laws watchdog found.
David Anderson QC was asked to evaluate the case for the tactics, which are included in the landmark Investigatory Powers Bill.
Mr Anderson's report, published on Friday, said bulk powers "play an important part in identifying, understanding and averting threats in Great Britain, Northern Ireland and further afield".
The techniques are used across the range of agency activity, from cyber-defence, counter-espionage and counter-terrorism to child sexual abuse and organised crime, the review found.
It concluded that there is a "proven operational case" for three of the four powers examined, and a distinct "though not yet proven" operational case for the fourth.
Mr Anderson, the independent reviewer of terrorism legislation, described the pace of technological change as "breathtaking".
His inquiry recommended that a panel of independent academics and industry experts are appointed to advise on the impact of changing technology, and how the intelligence agencies could reduce the "privacy footprint" of their activities.
Bulk powers are among the most controversial tactics set to be covered by the new spying laws, which are going through Parliament.
They cover a range of techniques used to acquire information in large volumes. Data is then used to generate intelligence about threats that cannot be obtained by more targeted means.
The review looked at four bulk powers which can only be used by the three intelligence agencies:
:: Bulk Interception - Used to intercept the communications of individuals outside the UK. The review said this power was of "vital utility" and had played an important part in the prevention of bomb attacks, the rescuing of hostages and the thwarting of numerous cyber-attacks.
:: Bulk Acquisition - Used to access communications data - the who, when and where of an email or text message but not the content - in bulk. Only disclosed publicly in November last year, for MI5 it has "contributed significantly" to the disruption of terrorist operations, Mr Anderson's report said.
:: Bulk personal datasets -These comprise personal information relating to a number of people, the majority of whom are unlikely to be of intelligence interest. The report said: "We were shown their utility in identifying ... potential terrorists, including individuals who posed a threat to the London Olympics and to the UK in the wake of recent attacks in France and Belgium."
:: Bulk equipment interference - Equipment interference includes hacking into suspects' smartphones and computers, which is seen as increasingly important tool given the rise of sophisticated encryption. The report said the power has never been used, but a "thematic" capability has been used to identify dangerous extremists in Syria.
Mr Anderson's review found a "proven operational case" for the first three powers. On bulk equipment interference it said there is a "distinct, if not yet proven" operational case in relation to counter-terrorism and cyber defence.
Where alternatives to bulk powers exist, they are often less effective, more dangerous, more intrusive or slower, the report added.
Prime Minister Theresa May said the report demonstrates how bulk powers in the new Bill are "of crucial importance to our security and intelligence agencies".
She said: "These powers often provide the only means by which our agencies are able to protect the British public from the most serious threats that we face. It is vital that we retain them, while ensuring their use is subject to robust safeguards and world-leading oversight which are enshrined in the IP Bill."
Shadow home secretary Andy Burnham welcomed the report, and called on Mrs May and Home Secretary Amber Rudd to accept it "in its entirety".
Liberal Democrat home affairs spokesman Alistair Carmichael said the Government must table amendments to give effect to the recommendation for a new technical advisory panel.
No 10 said the Government is giving "careful consideration" to the report.