Communications play a vital role in the response to disasters and crises. However, existing communications infrastructure is often impaired, destroyed or overwhelmed during such events. This leads to the use of substitute communications solutions including analog two-way radio or unsecured internet access. Often provided by unknown third parties, these solutions may have less sophisticated security characteristics than is desirable. While substitute communications are often invaluable, care is required to minimize the risk to NGOs and individuals stemming from the use of communications channels with reduced or unknown security properties. This is particularly true if private information is involved, including the location and disposition of individuals and first responders. In this work we enumerate the principal risks and challenges that may arise, and provide practical guidelines for mitigating them during crises. We take plausible threats from contemporary disaster and crisis events into account and discuss the security and privacy features of state-of-the-art communications mechanisms.