The name of the Shaitan who disturbs during Salah (prayer) is Khanzab.
Uthman Bin Abi Al-Aas (رضي الله عنه) reported to Prophet Muhammad (صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ) about disturbances and problems in his recitation during Salah. The Prophet (صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ) informed him that the cause was a Shaitan named Khanzab. The Prophet (صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ) then instructed Uthman Bin Abi Al-Aas (رضي الله عنه) on how to deal with this disturbance.
Therefore, if someone experiences distractions or negative thoughts during prayer, it is attributed to the influence of Khanzab.
