If your telephone bill was unusually high last month and noticed several unknown international numbers printed on your bill, while nobody in your house would call those numbers, this could mean that you have been modem-jacked.
How it happens?
If you are visiting a website, and suddenly prompted to download a programme, be cautious! You may be downloading a programme that disconnect your computer from your local internet service provider (ISP) connection and then reconnect your connection to an international number. So instead of enjoying your normal internet access charge, you are paying more for calls made to international destinations without your consent or knowledge.
This usually happens when your access supposedly 'free' international content sites like adult entertainment, gambling, gaming or music sites. Once you click through, they will disconnect your computer from your local ISP and will instead automatically linked your computer to an international ISP via direct dialing to that server. This will result in IDD call charges being reflected in your following month's phone bill.
However there are several ways your can take to reduce the risk of modem jacking happening to you.