In her living room, Ms. El Aroud, a 48-year-old Belgian, wears the ordinary look of middle age: a plain black T-shirt and pants and curly brown hair. The only adornment is a pair of powder-blue slippers monogrammed in gold with the letters SEXY.

But it is on the Internet where Ms. El Aroud has distinguished herself. Writing in French under the name “Oum Obeyda,” she has transformed herself into one of the most prominent Internet jihadists in Europe.

She calls herself a female holy warrior for Al Qaeda [1]. She insists that she does not disseminate instructions on bomb-making and has no intention of taking up arms herself. Rather, she bullies Muslim men to go and fight and rallies women to join the cause.