If you had a trojan or virus some other attack on your machine and you believe the integrity of your wallet is compromised then we recommend:
- Use your 12-word Daedalus wallet recovery phrase to recover your wallet on a machine that you trust
- Then you create another wallet and choose a different 12-word Daedalus wallet recovery phrase
- Move your ada from your old wallet to your new wallet.
- Discontinue using your old wallet.
It would be best if you did this as soon as possible to reduce the chances of losing your ada.
You can download the Daedalus wallet here: https://daedaluswallet.io/#download
See also Tips for Staying Safe Online