This is such a difficult topic. When I started my undergraduate in CompSci, the department of 300 students had exactly 3 women. The faculty had way more female instructors than it did students. The Commucation Sciences department, which was on the same campus, had the inverse student population. I'm all in favour for letting students making their own study (and career) choices, but when the imbalance is this great, I…
But the barrier is already low - you need to complete an undergraduate degree in a related field. That's it.