With mindcontrol you have a more problems to solve:
- the way, to connect sender and receiver
- the level of details of manipulation (from fear to exactly contracting selected muscles)
- the lasting of it (from just live stream to life long modifications)
- how many sender exists and how are commonly treated (from occasional hunted witch to nearly everyone normal)
- maybe also the receivers can be only spare or nearly everyone is at the risk
Let just use picture of internet - nearly any computer is connected, be it PC, laptop or smartphone - nearly none of it is supposed to be "fully commanded by unauthorized person", but hacking happens (and usually via programs not supposed to give control to anybody else - browsers, email clients, clocks, ...). User of hacked device may be aware about it and fighting it, but may be able to overcome it. Or may be full unaware. You can use this model for mind control too.
1.1. the simplest is "shared part of mind" somewhere outside our reach, where common ideas came from, but over eons every species developed "firewalls", that protects them from nearly anything, leaving just a small and "semicontrolled" ways to interact - dreams, sense of something bad happened, and so. But some individuals somehow found way around and are (willingly or not) to use some "hole" in the firewall and access victims inner mind. But it is nearly as bad as magic. Possible full range of actions and results.
1.2. brains use electricity, the waves can be detected, attacker is able to send its own waves and modify victims waves to affect her mind.
220.127.116.11. it can be natural, the range would be really limited and it is hard to explain, how it developed
18.104.22.168. it can artificial, the range can be much longer, if enough energy is available
22.214.171.124. attacker can have powerful transmitter
126.96.36.199. victim can have sensitive receiver
1.3. the brain use some sensors, (eyes, ears ...) which are used to transfer the signal - problem is with distance, on which such sensors can be affected
1.3.1 Natural ways - infrasound makes fear, big sharp tooth makes fear too, big round eyes make cute, innocent and attractive look, regularities are nice, irregularities are repulsive ...
188.8.131.52. Attacker may be able to alter his face/voice/scent/... in subtle ways to affect victim by this to push her to wanted state of mind - limited reach and hard to get precise control
184.108.40.206. Attacker can develop ways to overcome recognition and send messages directly in by some hole (equivalents of crafted packages, like Ping Of Death, or Buffer Overflow) - it is complicated as the signal is interpreted many times, before it reach the central mind, so it should have hack each and every level on the way in
220.127.116.11. Sumbliminar affecting - whispering to sleeping person "must kill Bill" and such
1.3.2. Artificial ways
18.104.22.168 - mass - use of TV propaganda or "every 30 frame is message" or similar ways
22.214.171.124 - direct - crafted phone calls, body enhancements (like modified voice, facial moving mask and so)
126.96.36.199. indirect - let suppose, that (nearly everyone/supposed victim/...) have implanted any artificial device, which can be hacked and used to send some signals to neural system. In near future at least mobile phones can be so popular and constantly used, that at least BT speakers would be implanted. Or even better also some visual stream like google glasses. This way victim can be directed precisely by phone number/IP/... and using bugs/zero day holes/viruses/infected SW/any other popular method attacker get direct access to its victim neural system. As it bypasses usual interface, it can do anything. Over any distance. Like a classical computer virus.
2.1. subtle - just make adrenaline raise, shock victim if misbehaves, make it spasm or anything other unwanted if it does not do, what you was, make victim happy, relaxed, or otherwise feeling good if she obeys and over some time you can train she anything you want - slow, not precise, but relatively simple method
2.2. alter her senses, that she see someone as monter and attack just from being scared of him
2.3. alter her memory/mind - make her "remember" that someone is her cruel enemy, which must be destroyed at any cost
Those way make victim behave "on her own will" but maybe "again her better judgement" - like it happens even now many times with abused, drug users, mentally ill, or just any other way manipulated people "I know, he is cheater, but I have to return to him and try to make him better", "I know I should not drink and my head will hurt at morning, but one more whiskey anyway", "I can't help myself, but I must eat this chocolate, even if I know I will cry over it in ten minutes"
2.4. if you can get deeper, you can trigger learned reactions - like send "attack", "run away", "sleep", "freeze", "lay down" and make the body react before mind came realize, what happens - and eventually override the victims commands totally
2.5. the hardest is manipulating the muscles directly - as you need issue really specific and complex commands and probably have also good feedback, otherwise the victim would just fall after two steps.
3.1. direct commands - victim "works" only under direct control, attacker have to make her every one move specifically - (point 2.5. leads here for example)
3.2. immediate action only - attacker issue simple command ("run away", "come here") and victim fulfills it, but then is free to do anything, until next command. Also she can call for help while doing the command ("Somebody please stop me now"), until commanded to be silent - this is typical where direct visibility is also request.
Attacker can issue such commands in voice (and fully detailed) "Came here and give me the key you got from John" (like a total authority figure), or by other means (maybe gesture, grimace, but then it is not so specific)
3.3. long lasting (altering mind/memory mainly) - victim then would attack anybody in blue shirt any time she see somebody like that. Maybe it would fade away in days/moths, maybe it would be permanent
- and 5. affects the world balance:
4.1. one of few attackers exists - they got their power from somebody (mad scientist, old chinese monk, developed spontaneously or such) and probably will end else hunted (Frankenstein), town/state/world leader/ruler (dark wizard king) or willingly hiding from public
4.2. large group exists - world must react somehow on it. Such group may be genetically modified, or some blood heritage, small nation, or something like albinos, or red-heads.
4.3. nearly everyone is able to mind control - like nearly anyone can physically attack in current world (maybe except small child or some minorities)
5.1. Only 3rd son of 3rd son can be mind attacked
5.2. Only 15-18 years virgins
5.3. Anybody ill, tired or with predisposition
5.4. Just anybody (maybe except few) can get computer virus
I would probably prefer model with (mad scientist, or some group like Illuminati) have a device (or altered brain, that they can do it) and the mind control is only on near range/direct vision with 3.2. immediate action only, where victim can be anybody (but few naturally resistant or shielded), so the world would be like ours, maybe with super villains and superheroes.
The other good combination is, that nearly everyone have implanted telephone, so is hackable, nearly everyone possibly can hack, but it is not easy, as good firewalls and regular updates makes defense really strong and attacker need a lot of knowledge and skills to be able hack on high level. (But spammers and script kidies are relatively common, as not updated firewalls are). Control is usually immediate action, as it is the most simple, but all range of attack are possible, but much more difficult (only few can construct false memories, that lasts normal checks, or puppet somebody around with direct control, as it is extremely difficult to do, not to deliver)
This is world of Ghost In The Shell for example, or more powerful Shadowrun, reflecting the current world of PCs connected to internet. Many get a little hacked, but usually without much loss (except for some money, privacy and similar non fatal problems), but on higher levels (business, government, celebrity) the war is much stronger, as there are much less targets, much more to obtain and much higher skills required to have a chance try to attack.