It's the kind of thing you learn as a kid in Australia. It's super common to have "red back" spiders under rocks, logs, or pretty much any object that's stationary on the ground for more than a few days.

Red back spiders are poisonous, evil looking little buggers! ;)

https://en.wikipedia.org/wiki/Redback_spider

Funnel web spiders are a thing as well, but they seem to be less common here in Victoria (south eastern Australia). Red backs though are everywhere.

https://en.wikipedia.org/wiki/Australian_funnel-web_spider