The file is full of 0xFF... Almost, because there are some 0xFE bytes in it.

```
FF FE FE FE FE FE FF FE FF FE FE FE FF FF FF FF FF FE FE FF FF FF FF FE FF FE FE FE FF FE FE FE FF FE FE FE FF FF FE FE FF FE FF FE FE FE FE FE FF FE FE FE FE FF FF FE FF FE FE FF FE FE FF FE FF FE FF FE FE FE FE FE FF FE FE FF FE FE FE FF FF FE FE FF FE FF FF FE FF FE FF FE FE FE FE FE FF FE FE FF FF FE FE FE FF FE FE FF FE FE FE FF FF FE FE FF FE FF FF FE FF FE FE FF FE FE FE FE FF FE FE FF FF FE FF FF FF FE FF FE FE FE FE FE FF FE FE FE FF FE FF FE FF FE FE FF FE FE FE FE FF FE FE FE FE FF FF FE FF FE FF FE FE FE FE FE FF FE FE FF FF FE FF FE FF FE FE FE FF FF FE FF FF FE FE FF FF FF FF FE FF FE FF FE FE FE FE FE FF FE FE FE FF FE FF FF FF FE FE FF FF FF FF FE FF FE FE FF FE FF FF FF FF FE FE FE FF FE FE FE FF FE FE FE FE FF FE FE FF FE FE FF FF FE FE FE FF FE FE FF FF FF FF FE FF FE FE FF FE FE FF FF FF FE FE FF FF FE FE FF
```

By converting this to binary (FF = 0, FE = 1), you'll get the flag:

`}paws_ym_ni_gniod_uoy_era_tahw{galf`
or
`flag{what_are_you_doing_in_my_swap}`