Avira Mac Security fully supports MAC OS X 10.9 (Mavericks) since version 2.0.1 (Update 1). If you are already using version 2.0 of Avira Mac Security, just make sure that you perform updates regularly to receive the latest updates. For further information regarding the Update 1 please see the Changelog.
If you are still using version 1.0 of Avira Mac Security please update to the latest version 2. All required steps are described here.
If you are not sure which version of Avira Mac Security you are using please perform the following steps to retrieve your product version: