As to invalid txs with invalid key_images. There are 7 in the blockchain. Thanks to zoidberg's fix it's completely fixed now.
Invalid txs:
Invalid key image: <26e8958fc2b227b045c3f489f2ef98f0d5dfac05d3c63339b13802886d53fc05>, amount: 0.990000000000, tx: <9f395234de50d836337dacef0133031f34d7ccf77ff261fdd710494675383e69>
Invalid key image: , amount: 0.990000000000, tx:
Invalid key image: <26e8958fc2b227b045c3f489f2ef98f0d5dfac05d3c63339b13802886d53fc85>, amount: 899.980000000000, tx:
Invalid key image: <0000000000000000000000000000000000000000000000000000000000000000>, amount: 899.980000000000, tx: <6130a0cbc7a19ba662d7bef35cd07bb948045e5d942d8db699748d781b2a73a4>
Invalid key image: <0000000000000000000000000000000000000000000000000000000000000080>, amount: 1799.990000000000, tx: <9584905ab31a2cda1ee2def9a853b02103cd66af67c9c525762e031ed7fa8d96>
Invalid key image: , amount: 1799.990000000000, tx: <8b02b0477493f6d86c7f9067ada619bb877faedc7d4312f3947ff8b67cc4422b>
Invalid key image: , amount: 1799.990000000000, tx: <38999f6326860e4f48543c978a3f79e135d8ff0e7ce2ad5f5f169d455ecbcd6e>
Invalid txs with relation to blocks and timestamps:
tx amount block timestamp
9f395234de50d836337dacef0133031f34d7ccf77ff261fdd710494675383e69 0.99 757131 2017-04-10 22:54:06
ff43d5b09e49d619a14ea243ebc2640a187813b2afd67f1090da948204b949c2 0.99 757134 2017-04-10 22:58:09
d2a66d7dc40b8a618d15f878c9153a61d0a87dde703df8185f41b0c6078d0a56 899.98 757183 2017-04-11 00:03:48
6130a0cbc7a19ba662d7bef35cd07bb948045e5d942d8db699748d781b2a73a4 899.98 757190 2017-04-11 00:14:17
9584905ab31a2cda1ee2def9a853b02103cd66af67c9c525762e031ed7fa8d96 1799.99 757235 2017-04-11 01:05:33
8b02b0477493f6d86c7f9067ada619bb877faedc7d4312f3947ff8b67cc4422b 1799.99 757237 2017-04-11 01:10:58
38999f6326860e4f48543c978a3f79e135d8ff0e7ce2ad5f5f169d455ecbcd6e 1799.99 757241 2017-04-11 01:13:46
As you can see, an attacker tried with small amount tx, then went further.
It was performed in ~2 hours at April 11th midnight.