what can you do to keep spies out. I am sure that the more land you have the more difficult it will be to spy, but does your spy tech and number of spies help?

Yes. The attackers Spies/Land, also known as Spies Per Acre of Land (SPAL) is compared to the defenders and the ratio determines the chance of success.

Actually the more land the defender has the lower his SPAL is, so it makes operations against him more likely to succeed.

Spy tech increases the effective number of spies. If you had 100k spies on 10k land and 120% spy tech your effective SPAL would be 100k/10k * 1.2 = 12

still with enuf tries even 10 spal country can spy 100 spal country