The Drupal core ! (ok not complete, but almost).
Again, sorry for the dark photo.
Also on this photo is David 'Kat' Monosov (the first on the left). He gave an very interesting presentation on scalability and security. The things I remembered:
- Of the 1000+ co-located servers about 50 or more per week are hacked !
- Don't trust the contributed (non-core) modules on security too much.
- Drupal Core is relatively secure (everything is relative and nothing is secure anyway).