41 percent of women say a partner has spied on them online.
Researchers conducted a survey for the domestic violence charity Women's Aid and found one in three women say they've been harassed online.
More than 40 percent said that their current partner or ex has monitored their online activity, 37% said they felt threatened by it. But when asked if they had been stalked, only 30% of women agreed.
The charity says this may be because of a lack of awareness that online spying constitutes harassment.
Facebook and email were named as the most common ways women were spied on. The researchers warn that not every anonymous note women get online is romantic.