Well being trained properly is the best advice as there is nothing more risky than thinking you are clean and are not. It was on foot in a busy city so it's way too much to write up here but if your interested in reading basic stuff from a general security guide follow the link in my bio.
That would be considered very suspicious and alert the team immediately, plus they would have been trained to deal with that. I had no reason to feel threatened by them as I haven't done anything wrong. I just used the chance to practice some past training, buy myself time to figure out WTF was happening then broke off at a point where that would seem legitimate to them without them sensing it was what I was doing. It may well have been a genuine criminal investigation I'd somehow walked into by accident so I had no desire to compromise that.
It's really a sort of long story and depends ultimately on the risk that you potentially face and their possible objectives.
Roughly the way to think about your options are:
-Covert - Use your detection of one or more to detect more of the team but do nothing. This preserves your ability to detect them in future especially if they reuse tactics and locations, especially any trigger locations that they pick you up on.
-Overt - Use your detection of the team to openly "burn" them by confronting them ("Who the fuck are you and what do you want?"). But that means in some contexts like a human rights defender they may move in to arrest you, kidnap or whatever depending on their objectives. Or they will just step off you and come back next time in a better way that means you won't be able to detect.
-Semi-overt - increase their heat state by approaching them for something innocuous ("Hey do you know where the local church is?"). This means you test their local knowledge and that individual will most definitely lift off you for awhile though may not entirely suspect what you did was deliberate as they would above. They could of course use that time to threaten you, especially if you are talking criminal or narco threat etc.
-Overt break - You use a very obvious method of breaking away from them like jumping a light, speeding up your normal walking pace, swapping public transport, going into a location that doesn't fit your pattern of life purely as it would be hard to cover and then ditching out fast through an exit etc etc. Again that will alert them and as above they may move to snatch you or come back another time. Remember, they may already know where you live/work etc so they may have that information.
-Covert break - You run an SDR then find a location you can use that fits your pattern of life and use that to lose them. They can still of course come back but they may chalk it down to an accidental loss if you do it right. Plus you are sometimes playing on their cultural biases that means they may be reluctant to report a loss to their bosses etc.
There's obviously a hell of a lot more to think about. Such as if you use the above to create a break, what is it you are going to do then? This is often what people struggle to think about in advance, especially as its intimidating as hell to find yourself in that sort of scenario with a real threat. For example people we've worked with have made decisions to essentially go on the run with just what they have in their pockets (from people looking to kill them) once they broke away. That's when the training about the physical and digital stuff (alert help but may need to ditch the phone, get grab bag, change clothes, switch to routes off CCTV etc etc etc) kicks in.
What is useful though is that you as the person being followed usually have control over who, what, where etc happens in your day (unless it's an intimidation scenario like in some countries where surveillance literally waves at the people every morning as they follow them around).
Never thought I would see someone referring to the use of SDRs - let alone effectively applying one - on HN. Curious as to where you picked up the skillset.
Mostly private courses and experience built up over the years driven by the need to use and train on it for journalists and activists at risk.
On a few, thankfully limited occasions I've had to use it in relation to myself where a real threat existed but rarely enough. Mostly when I've had to use it personally it was to ensure I wasn't risking anyone I was meeting or if I wasn't sure if they might be a deliberate/accidental security threat.
We teach it on some of the source protection training courses with do with journos/NGOs. Also we write some basic stuff about it in our open source app, Umbrella. Some activists are threatened by actors ranging from kidnap to ISIS, from corporate to government intelligence, from crime to stalkers. So it's very useful for helping people identify a wide range of threats early.
Also just generally for getting peoples heads up out of their phones and off the ground and taking in more alertness of their surroundings - the sort of Coopers Colour Code style thinking.
Very cool! Sounds like some really fun training to provide and never even considered how useful those skillsets would be for journalists. Thank you for sharing.
What did this entail?