Dreaming of attacking snakes is a bad omen as per dream meaning and interpretation. The dream means that you will see a friend or someone close to you turning your enemy and you will be force take attacking or defensive action.
The dream is asking you to be careful about all your dealings and you should avoid trusting people blindly.
Dream of attacking snakes is also a sign of unfortunate incidents in life or bad luck.
Please note that a dream to have meaning it should happen naturally. If you dream about it after watching or reading or talking about during day time then it does not have any meaning.