What determines the quality of items obtained from a portal hack?

As we found out today loot item quality depends on the following things:

• Portal level - the higher the better
• Level of the strongest resonator (I believe it determines the maximum item level you can get from the portal, not confirmed)
• Player level. We made an experiment today L1 and L6 players hacked the same L4.75 portal several times today:
  • L1 player's loot consisted of L1 and L2 resonators and XMP + common shields
  • L6 player's loot mostly consisted of L4 items + several L5 and L6 items + rare and very rare shields.

The higher the level of the portal, the better the stuff coming out. For example, an L4 portal will give you L6 resonators/bursts (and that was from an enemy portal).

The level of gear available from a portal is based on the minimum of the portal level and the agent level, which I call the hack level. The hack level also determines the number of symbols and time constraint for glyph hacks. which backs up this claim. From my experience you can get get resonators of the hack level +/- 1 level, bursters of +/- 2 levels, and cubes at the level of the hack. The distribution within those ranges seems to favor mid level gear (ie. a lv3 hack will get more lv 4 resonators than lv 2 resonators, but a level 6 hack will get more lv 5 resonators than lv 7 resonators)

The amount of gear drops seems to be less from enemy portals (though the distribution may be different depending on the resource; some claim viruses are more common from enemy portals, and during the thee weeks before the second anniversary bursters were much more common from enemy portals)