Word for "influencing or manipulating people without their knowledge"

Maybe not the perfect fit, but the verb to exploit seems like a word that's very close to the one you're looking for:

make use of (a situation) in a way considered unfair or underhand.

Your example:

Social Media content is exploiting people's opinions.

Machiavellian overlaps with both 'underhanded / deceitful / devious' and 'manipulative', as attested at this entry at Thesaurus.com. 'Perfidious' and 'treacherous' also spell out the deceit involved. These are of course adjectives rather than verbs.

CollinsCoBuild gives:

If you describe someone as Machiavellian, you are critical of them because they often make clever and secret plans to achieve their aims and are not honest with people.

And HarleyTherapy:

Machiavellianism in psychology refers to a personality trait which sees a person so focused on their own interests they will manipulate, deceive, and exploit others to achieve their goals.

In broadened usage, 'Machiavellian' relates to the behaviour as well as the character trait; thus there are examples of "Machiavellian attempt" and "Machiavellian methods" on the internet.

This broadened usage is licensed by M-W:

Machiavellian: suggesting the principles of conduct laid down by Machiavelli; specifically: marked by cunning, duplicity, or bad faith

He relied on Machiavellian tactics to get elected.

ODO also has relevant examples:

... while fending off the Machiavellian manoeuvres of others

... repressive conventions of the times and the Machiavellian politics of those around her

... a Machiavellian game of political ping-pong.

The word "Warp" could be used, as in weather warping, or allowing to twist out of square, lumber that is left outside in wet weather.

"The lack of context, critical thinking or historical background in Social Media's presentation of issues is warping the peoples opinion's".

I believe exploitation of this condition is done subsequently but does not describe this activity.

I want to suggest sway:

Control or influence (a person or course of action)

Here are three examples from Oxford living dictionaries:

• ‘This story absolutely outraged me and it is stories such as these that sway people over to thinking that capital punishment should be used on some criminals.’

• ‘Did he influence Clara, or did she sway him in their initial decision to keep the concerto hidden?’

• ‘How is it that you could easily sway Father when me and Brian have to literally beg for what we want?’

And there are more example on the internet

Surreptitiously (ODO)

• Obtained by ‘surreption’, suppression of the truth, or fraudulent misrepresentation;

• Taken, obtained, used, done, etc. by stealth, secretly, or ‘on the sly’; secret and unauthorized; clandestine

So,

"Social Media content is drastically and surreptitiously influencing peoples opinions (without their knowledge)".

Mesmerising is the word I would use.

"Social Media content is mesmerising people without their knowledge".

Franz Mesmer (1734-1815)... who theorised that there was a natural energetic transference that occurred between all animated and inanimate objects that he called animal magnetism, sometimes later referred to as mesmerism.

Wikipedia

The Internet Is Mesmerised By This Video Of A Snake Sipping Water

NDTV

3. trans. To affect (a person) as if by hypnosis; to fascinate, hold spellbound.

1986 B. Fussell I hear Amer. Cooking ii. viii. 115 Froggers work in pairs, one to mesmerize the frogs..with a spotlight..the other to catch the frog by his legs.

1995 Independent 4 Mar. 25/2 There were his London superiors, mesmerised by the apparent profits he was making.

OED

"The word gaslighting is used to describe an attempt to destroy another's perception of reality."

And in the play which originated the expression, Gas Light, the gaslighter was a bigamist and jewel thief who manipulated his wife into not obstructing his attempts to recover a score.

It's typically used to describe abusive intentions, but (in my experience) has unfortunately loosened to include other attempts to shift the perceptions of others until they match what the manipulator wants them to believe. Either way, I am completely convinced that the social-media activity which you're asking about is indeed deliberately abusive and I find that "gaslighting" to be a very apropos description of what the perpetrators are doing.

https://en.wikipedia.org/wiki/Gaslighting

Question: What is the word that describes the process of influencing people without their knowledge?

From Oxford Dictionary:

Propaganda NOUN 1. mass noun : Information, especially of a biased or misleading nature, used to promote a political cause or point of view.

Origin Italian, from modern Latin congregatio de propaganda fide ‘congregation for propagation of the faith’ (see propaganda (sense 2)).

propaganda (sense 1 [cited above]) dates from the early 20th century.

From Wikipedia:

Propaganda is information that is not objective and is used primarily to influence an audience and further an agenda, often by presenting facts selectively to encourage a particular synthesis or perception, or using loaded language to produce an emotional rather than a rational response to the information that is presented.1 Propaganda is often associated with material prepared by governments, but activist groups, companies and the media can also produce propaganda.

In the twentieth century, the term propaganda has been associated with a manipulative approach...

Noam Chomsky: Propaganda and Control Of The Public Mind (full lecture on Youtube).

You can alternatively use the term brainwashing.

Collins defines brainwash as:

verb, transitive, US;

[T]o indoctrinate so intensively and thoroughly as to effect a radical transformation of beliefs and mental attitudes

To instill, according to Cambridge Dictionary:

to put a feeling, idea, or principle gradually into someone's mind, so that it has a strong influence on the way that person thinks or behaves

Attribution:"Instil Meaning in the Cambridge English Dictionary." Cambridge Dictionary. Accessed April 05, 2018. https://dictionary.cambridge.org/dictionary/english/instil.

I would use the word indoctrination or indoctrinate.

From Wikipedia:

Process of forcibly inculcating ideas, attitudes, cognitive strategies or a professional methodology by coercion.

The word applies to systemic manipulation, so wouldn't be appropriate if you're just describing particulars on social media. However, given the way social media algorithms specifically curate content that reinforces the viewer's particular worldview (and even biases it according to some), it's entirely appropriate if you're criticizing social media generally.

---

Social Media content is indoctrinating people without their knowledge".

I would suggest hoodwink:

Deceive or trick. ‘staff were hoodwinked into thinking the cucumber was a sawn-off shotgun’

Oxford

"Social Media content is drastically influencing peoples opinions without their knowledge".

I would use: "Social Media content is drastically influencing people's opinions unbeknownst to them".

Robert Goodin observes that manipulation carries “especially strong connotations of something sneaky” and that manipulation characteristically happens unbeknownst to its victim.

There are tons of references out there that collocate with manipulation. I have only given two.

The term specifically means without the knowledge of the person specified.

Merriam Webster - unbeknownst, aka, unbeknown

unbeknownst

unbeknownst

"Social Media content is drastically influencing peoples opinions inconspicuously".

ODO:

inconspicuously

ADVERB

See inconspicuous

‘He's less keen on persuading you with his big ideas than simply putting them out there - and having done that he seems to slip out the door quite inconspicuously.’

inconspicuous
ADJECTIVE
Not clearly visible or attracting attention.

A lot of good answers already, but I just wanted to add bias. As in:

Social media biases peoples opinions

Bias is more scientific and comes in many forms as this infographic shows.

Depends 'what' the writer is wanting to convey. Consider the 'effect' on people is of greater import than Social Media. Perhaps re-arranging the sentence to emphasize this import would provide clarity.

Examples:

1. Peoples' opinions are being unknowingly and drastically influenced by Social Media.
2. People are unaware that their opinions are being drastically influenced by Social Media.

Inception? Though I think it's not really in the dictionary (do correct me if I'm wrong), encapsulates what you have described. I think a more apt word may be "charm" or "subtle insinuation".

Social engineering is a term for influencing or manipulating people without their knowledge. It can be used in a general sense, or in a context specific to information security. This question seems to be asking about general usage.

Social engineering is defined as:

efforts to influence particular attitudes and social behaviors on a large scale, whether by governments, media or private groups in order to produce desired characteristics in a target population.

Influence campaigns are a prominent application of social engineering. The objectives of such campaigns are not necessarily neutral or beneficial for all parties involved, although they can be. Examples include:

• the coordinated use of social media to affect outcomes in electoral politics
• improving health care outcomes or responsible savings for retirement by reinforcing recognition of long-term thinking over impulsiveness

The UK Behavioral Insights Team (under David Cameron) and US Social and Behavioral Sciences Team (under Barack Obama) were known as “nudge units”. They used behavioral science techniques for government policy. Via Nudges: Social Engineering or Sensible Policy? (Psychology Today), "The underlying philosophy behind nudges is libertarian paternalism: people should be free to make the decisions they want, but policymakers can present these choices in ways that lead to desired outcomes."

Social engineering generally has a negative connotation, of propaganda and deception, regardless of the ultimate goal. In this article by public accounting firm Deloitte and Touche, regarding behavioral psychology, social engineering is likened to manipulation. It is not necessarily an unmitigated force for good:

Many object to the idea of using psychology to nudge people’s behavior on the grounds that it is manipulative or a form of social engineering. These concerns are crucial and not to be swept under the carpet. At the same time, it is possible to view both behavioral data and behavioral nudge science as tools that can be used in either socially useful or socially useless ways. Hopefully the examples discussed here illustrate the former sort of applications. There is no unique bright line separating the usefully personalized from the creepily personal.

Subversion.

On a basic level, the subliminal process you're describing can be characterized as the Machiavellian SUBVERSION of traditional Western, Judeo-Christian values and free market society to indoctrinate, bias, sway, or otherwise brainwash people through mesmerizing media propaganda, historical gaslighting, and surreptitious social engineering to inconspicuously warp public opinion, exploit and hoodwink the masses, & further instill the consolidation of power and control into the hands of a small, elite ruling class. Other explanations are one or more of the following: unbeknownst ignorance, ego/bias, noise narratives, convenient dismissals of truth, or lesser derivatives of the aforementioned framework. This has been the revolutionary goal of the Fabian Society, for example, since its inception in the 1880s.

Now that we are aware of the ailment, how do we treat and destroy the disease?