Social networks, whether they are for private or professional matters, make it easier for attackers to gain access to your personal data. A dense field of information allows attackers to manipulate their victims with personalized scenarios and force them to take harmful actions. This threat can concern individuals but also entire organizations.
Use another factor for authentication. Xing and LinkedIn offer a two-step signing in process where you use your password and receive a text message or authenticate your profile via app as a second factor.
Using more than one device for employing the factors would be even safer: e.g. you sign in via your laptop with your password and use an app on your mobile phone to authenticate.
You can authenticate your profile via app or text message. => settings / member account / two-factor authentication
Your phone number does not appear on your profile. If you want your phone number to appear on your profile, you can add it via your profile (edit business card / edit contact details).
On Xing, you have the following options to protect your privacy:
On LinkedIn, you have the following options to set the visibility of your profile and network: