Demons are living, conscious, purposive immaterial-spirit Beings; but computers are regarded as non-living material objects made of minerals, performing electrical and 'digitally-segmented' procedures.
How can demons influence - say - 'the internet'? This seems difficult, or impossible, to understand because, with the usual assumptions included in the question, we seem to be suggesting that immaterial living spirit can (somehow?) affect solid, dead matter.
We are falling back into asserting an incoherent or paradoxical 'ghost in the machine' scenario...
As usual, the problems are with false assumptions; assumptions that intrinsically pre-judge and have-excluded the very possibility under question.
Instead, these are some assumptions about reality which I take to be true, and which make sense of the idea of demons influencing the internet directly, by 'incarnating' into computational systems:
1. The spiritual is primary, and the material is a sub-set of the spiritual.
In other words, matter might be pictured as somewhat like 'condensed spirit'.
This means that all matter is spiritual, necessarily and unavoidably. So there is no 'problem' about spirit affecting matter, because all matter is 'within' spirit to-start-with.
2. The spiritual world exists as Beings - (is 'organized' as Beings) which are living, conscious, purposive entities.
So everything we might assume is a 'thing' is instead actually either 'itself'-a-Being, or part-of a Being.
So each Man is a Being; but (for instance) Man's bones, or veins, are (apparently) not Beings; but are parts of a Being.
If a tree is a Being in its own right, maybe a mushroom is part of a larger Being (containing many mushrooms linked underground). A mountain might be a Being, perhaps; or it might be part of a Being that is an island, a continental plate, or The Earth?
(We don't usually know the boundaries of Beings nor how they are organized, so I am simply illustrating the principle.)
3. A Being can form part of a larger Being, and often includes smaller Beings.
Men are Beings that contain Beings.
And example might be a white blood cell in our blood, which (we might imagine) has no idea that it is part of a human being! But simply lives-out its life in hunting cellular debris or invading germs, eating and assimilating them, reproducing etc.
And Men, as Beings, are contained-by other Beings.
For instance; a Man, whose life and activity forms part of a larger human grouping; a tribe, or maybe a nation about which he may be ignorant and which 'uses' his abilities and labour for its own purposes.
This means that a larger Being - containing Men - must be genuinely real (not just a convenient metaphor), and is typically a spiritual (not material) Being. In the past this was, when the Man-containing Being was Good, conceptualized as a presiding angel - when the larger Being is evil, it is a demon.
(Both might, and typically do, exist; contesting over the component Men - e.g. a national Archangel versus a Globalist demon; varying in dominance through time, and each group angel/ demon 'using' different Men, for different roles; and different selective aspects of those Men.)
What is happening here is that only a part of each component Man is truly a component of the larger Being that is the tribe or nation or whatever group it may be. The Man's essential Being is Not a part of any larger Being, but may choose to affiliate-with or reject that larger Being and its purposes.
What happens is that some of that Man's attributes are in fact being 'organized' into a larger unity; while the essential Being is eternal and cannot be assimilated-into any larger Being - but necessarily stands apart from all possible Systems, and decides whether or not to join-with them.
From the perspective of the larger Being; the component smaller Beings are organized into hierarchical and specialized functions, and used to perform particular tasks in particular sequences; analogous to the parts of an army - each operating under 'orders'.
Putting together the above three assumptions, we can see that the agenda of evil might be administered overall by a Being such as Satan, who is analogous to a general directing lower ranks towards a particular strategy. These lower ranks might include demons participating in a hierarchy of organized and specialized functions; the lower ranks also include Men - and other Beings and parts-of-beings such computers, programs, the internet...
While demons are supposed to be wholly committed to evil by their natures; the Men who participate in the System of evil are only partially being used for that purpose.
So a Man might regard his job as 'just' digging holes and building walls, or collecting and summarizing data in an office; and this activity might be integrated into an evil-orientated agenda... or a Good and Godly one; and to varying degrees.
Yet the situation is not static, and evil operates purposively to increase itself and corrupt other Beings; so the Man in an evil-aiming organization who digs holes, or the one that deals with 'information' - might be confronted-with links between his activity, and its aims and consequences.
So that he will become aware of his participation in evil, and then needs consciously to decide whether to endorse or repent this participation - each of which will have different consequences for how much of himself participates in the System.
(ie. If an aware Man then repents his participation, corruption does not proceed; if he refuses to repent and regards his evil as Good, he will be embracing the value-inversions of evil; then that Man will become more positively orientated towards evil goals.)
Anyway; to return to the original question of how demonic evil might use the internet to pursue its goals; we can see that there are multiple potential mechanisms, operating at all levels... (And bearing in mind that the-spiritual is primary, and the-material a manifestation of spirit.)
Planning the organizations which comprise 'units' of demons, Men, and other Beings/ parts of Beings such a computers and their programs...
'Personnel' decisions about which particular individuals or units are performing specialized functions within these systems (by directing the flow and sequence of tasks)...
There is the administration of these organizations, filtering their inputs and outputs, emphasis given to selected outputs etc.
Once any evil entity is within any organization, and that organization is regarded as running on the basis of un-influence-able material processes; then evil evil-orientated choices of evil-affiliated Beings will operate to increase the power of evil within that organization*.
As always, insofar as it is purposive, the demonic agenda is - to some, variable extent - either consented-to or chosen by those who participate.
Genuinely unwitting participation is possible - but since this is not corrupting, it is regarded by the ruling evil entities as merely a temporary phase, a means to the end of corrupting a Being.
Sooner or later, individuals participating in evil will be brought to awareness of the goals and direction of their role - and this moment will be engineered such that the individual is likely to conceptualize the evil he is doing as - inversely - actually a higher type of 'Good'...
As when architects are induced to embrace deliberate ugliness as actually a higher, more sophisticated kind of beauty; or politicians embrace the Big Lie as in-service-to a higher 'truth' - such as social justice; or when the enforced mutilation and poisoning of children is justified as part of a more-profound ethic of choice, liberation and inclusion.
In other words, demonic influence does not need to happen by such weird/ spooky ideas as a demon putting his spiritual-thumb into a software process to shape a particular outcome. Although, insofar as the electrical instantiation of a software process is a material part-of primarily spiritual reality; material action will manifest in accordance with spiritual realities; and then the outcome of processing will not be explicable within the System - (and will be put-down to some unknown 'random' error or failure).
In other words, the material is never independent of the spiritual; and the spiritual is always controlling the material.
The material elements of computers or the interest are already and always part of the life of primarily spiritual Beings; so, to posit their being subject to net-evil orientations is merely to assert that demonic spirits have become dominant, overall, in that particular aspect of this created earth.
*Note: This is why mainstream modern materialism - which fundamentally misunderstands evil and denies the reality of demons - leads inevitably to an incremental corruption of society. Once a demon has gained entry anywhere (and this is inevitable, sooner or later) he can operate undetected; his identity will be denied, and his effects explained-away as random errors or incompetence. This may be one reason why it was possible for prophets of the past to predict these End Times.