Set up your base report and add
tblAntivirus. Add
tblAntivirus.DisplayName to the list of fields in the report and set the criteria to "Not Like '%Sophos%'" (or whatever you need to match).
e.g.
Select Top 1000000
tblAssets.AssetID,
tblAssets.AssetName,
tsysAssetTypes.AssetTypename,
tsysAssetTypes.AssetTypeIcon10 As icon,
tblAssets.IPAddress,
tblAssets.Lastseen,
tblAssets.Lasttried,
tblAntivirus.DisplayName
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Inner Join tblAntivirus On tblAssets.AssetID = tblAntivirus.AssetID
Where
tblAssetCustom.State = 1
And tblAntivirus.DisplayName Not Like '%Sophos%'