The European Court of Human Rights has ruled that it may be permissible to monitor an employee's use of the internet, subject to the principles of proportionality and reasonableness. In this particular case, the claimant set up a Yahoo Messenger account for professional use but used it to send private emails to his brother. When the employer discovered this, the employee was dismissed. 

The Court found by a majority of six to one that the domestic courts in Romania had struck a fair balance, within their margin of appreciation, between the applicant’s right to respect for private and family life, the home and correspondence under Article 8 and his employer’s interests.

The ECtHR concluded:

"While it is true that it had not been claimed that the applicant had caused actual damage to his employer... the Court finds that it is not unreasonable for an employer to want to verify that the employees are completing their professional tasks during working hours."

One judge dissented. He considered that the employer went too far in this particular case, in that it accessed his personal and professional accounts. Further, "...the employer’s interference had wide adverse social effects, since the transcripts of the messages were made available to the applicant’s colleagues and even discussed by them. Even if one were to accept that the interference with the applicant’s right to respect for private life was justified in this case, which it was not, the employer did not take the necessary precautionary measures to ensure that the highly sensitive messages were restricted to the disciplinary proceedings. In other words, the employer’s interference went far beyond what was necessary."

http://hudoc.echr.coe.int/eng#{"documentcollectionid2":["GRANDCHAMBER","CHAMBER"],"itemid":["001-159906"]}