I found a picture of what they look like on Google.

http://3.bp.blogspot.com/_Z_Us2xEQ9t8/SR05N8BwN2I/AAAAAAAAFFM/5_11F3cIHjQ/s400/strawberrywormDSC01743w.JPG

When they attack, you see nothing but a little hole on the outside. And they eat from the inside out.

Perhaps slugs?

Nope, they're definitely worms. They wiggle around and move fast. See the link, this is exactly what they look like.

Here is a link that might be useful:

I say eat them worm and all. Who knows, might be the tastiest strawberries ever. Please report your findings.

All kidding aside, is it seriously every strawberry? I've had these worms along with other pests like slugs and pillbugs attack the strawberries when they were close to the ground.
You may want to try putting some coarse mulch around the plants such as straw or wood chips to confuse the critters making it hard for them to find the berries.

Here is a link that might be useful: www.PhotoLandscapeDesign.com

It is not every strawberry,but I'd say around 75% of them have the worms in them.

I'm not too keen on eating worms (haha!) I'll try the mulch idea!

Are there any organic pesticides I could use?

I got such worms inside some of my cabbages.
I think that they are red composting worms. Several years ago i bought red composing wors when i was playing with worm bin. These worms managed to escape in the garden.

I am planning to use pine needles next year.