The Metropolitan Police said the unit, codenamed Project Alpha, had already prevented “threats to life” and helped stop a string of copycat robberies targeting JD Sports.
Senior officers said it is already conducting work for five other British police forces and aims to build the same capability across the country.
“We want to be on the front foot of open-source intelligence,” he told journalists at Scotland Yard on Wednesday.
“This is about understanding what is a threat now, what is a threat today,” he added.
“We are stopping serious offending happening, serious violence, firearms-related crime, knife-related crime, knife sales, drug dealing on Snapchat and Instagram at scale.”
The team has also detected plans to attack inmates and import drugs into prisons, the officer said, adding: “It’s all out there.”
Set up in June, Project Alpha has already dealt with 800 taskings.
Eight officers, mostly under the age of 25 and born in “challenging” areas of London, are currently dedicated to the unit.
“Their insight is fantastic and their skills on social media are second to none,” T/Det Ch Supt West said.
“They spot threats in a different way. The terminology used by gangs, the differences between south London and north London, and the type of slang used.”
Police said while some threats – like those seen in drill music – are overt, codewords can be used to conceal illegal activity.
In one case, detectives discovered liquid cannabis was being infused into sweets and sold over social media using a codeword spread on WhatsApp.
Project Alpha also helped stop a spate of looting targeting JD Sports branches earlier this year.
The trend saw teenagers – some armed – storm shops in locations including Tottenham, Croydon and Stoke-on-Trent while wearing hoods and masks and flee with looted clothing.
After videos were shared on social media in October, apparent copycat incidents were reported in the Netherlands and Belgium.
Police said Project Alpha picked up online “chatter” before the raids hit the news, and predicted the next targets.
“They scanned Snapchat and Instagram and found where the next wave was going to happen,” T/Det Ch Supt West said.
“By working with JD Sports, we were able to up security at shops and the offending stopped within 24 hours.”
He said the project had evolved out of a crackdown on drill music videos that started in 2015, and has forced violent tracks onto niche platforms and porn websites.
T/Det Ch Supt West said over the past two years, the number of threats used in drill music had decreased as its commercial success had risen.
Project Alpha officers have been engaging with the operators of online channels that promote the tracks in an attempt to draw the line between artists expressing their experiences and directly inciting violence.
The government’s first ever Serious Violence Strategy, released in April 2018, said social media had created “an almost unlimited opportunity for rivals to antagonise each other” in ways viewed by a huge audience.
The document said videos and posts “glamorise weapons and gang life”, while inciting attacks and possibly leading to “cycles of tit-for-tat violence”.
The strategy was heavily criticised for omitting a leaked report by the Home Office warning police budget cuts had “likely contributed” to rising violence and “encouraged” offenders.
At least 129 people have been killed in London so far this year according to Metropolitan Police figures, which do not include last Friday’s terror attack.
Police said while stabbing numbers are broadly level, shootings have fallen by 35 per cent year on year following proactive operations against gangs and organised crime groups.