Is it permissible to sell non-confidential work data, for which the company did not pay, in order to reclaim a portion of rights usurped by the employer, taking into account personal use of the internet during work and obtaining data from a colleague without his knowledge?

It is not permissible to sell the office's data without the owner's permission, as this constitutes treachery. As for the issue of seizing financial rights, it does not apply here for two reasons: the first is that data is not known property that can be controlled, and the office owner might suffer greater harm than the questioner's right; and the second is the presence of a third party, the colleague, who might be harmed by this action. As for using the internet for personal purposes in the office during work, it is not permissible except with the explicit or customary permission of the office owner.