Germany head into Wednesday's clash in Durban on a high after Klose scored twice in a 4-0 drubbing of Argentina on Saturday.
The striker said that between a post-flight midnight snack and a mid-day training session on Sunday, he had watched a replay of Spain's 1-0 quarter-final win over Paraguay.
"Spain are certainly a better team than our previous opponents England and Argentina, they are a fantastic team," the forward said.
"I caught a rerun of their game with Paraguay, it was a great game but it showed that Spain are not invincible, not unbeatable. We have to filter out their weaknesses and then exploit them," he told a news conference.
A Fernando Torres goal gave Spain a 1-0 win over Germany in the European Championship final in Vienna two years ago but Klose expects a different kind of match.
"You can't compare the games, just as there was no way you could compare Saturday's game with Argentine with the game against them in 2006," he said. "These are different squads now, with different players.
"Spain still reigns supreme in Europe but in terms of quality I think we have improved considerably.
"We have introduced a fresh attitude and fresh blood. A few years ago people said that it was a shame that no attackers or creative midfielders were coming through (in Germany) but time has proved them wrong," he said.
One difference will be the presence of David Villa in the Spain attack. He is the tournament's top scorer with five goals, one more than Klose.
"He is almost as complete a player as Lionel Messi and like with Messi you have to combat him as a team not just with one player," Klose said.
Klose, who won his 100th cap on Saturday, brought his personal World Cup tally to 14 goals in three tournaments, level with Germany's Gerd Muller and one short of Brazilian Ronaldo's record total of 15 goals.
"I hope that he isn't too worried," joked Klose, "I never dreamed that I would get close to his record."
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