Beware of anyone cold calling you about your computer, claiming to be from a recognised brand name, specifically if they tell you that your computer has been infected with viruses/malware and that they ‘can see activity on their servers’ indicating that your computer is in need of maintenance. THIS IS A COMPLETE AND UTTER SCAM.
I can’t highlight enough how much of a scam this is, it is well recognised scam being run by a number of companies (we tracked one down to Montreal, but there are quite a few others). Not trying to be in any way racist, but most of the callers are either Indian or Pakistani, this is simply a statement of fact.
See information here from Microsoft on the issue.
In case you doubt that this is a well known scam you will find several videos on YouTube dealing with the subject.
Note that the company in question does not have to be Microsoft, it could also be Symantec, Norton, McAfee or any other well known brand, even a local one, just to give the victim the illusion of safety by the use of a well known brand name.
If you have been affected by such a scam it is advisable to contact the GardaĆ and advise them of any information given to the callers. If you have given credit card details to them then call your bank and have any direct debits stopped and any money expended refunded. It is a recognised scam so, with a little persuasion, this should eventually be recognised by the bank. They can take a little time to come around to this though as your particular branch may never have come across this scam before. Talking to Visa or Mastercard directly will often get better results.
After that you should get a properly trained technician, like our own, to examine your machine for any malicious code the callers may have had you load on to the machine. LogMeIn Rescue is often used (a perfectly valid and excellent piece of software under normal circumstances), but there are other programs that can be used toward the same ends.
See this Irish Examiner article on one such scam attempt which led to a threat to bomb an Irish Garda station.

