The U.S. Department of Homeland Security designated hotels as possible "soft targets" for terrorist attacks in 2001, and for good reason: since 2001, terrorists have attacked several hotels around the world, including tourist destinations in Jakarta, Israel and Jordon, according to a Conde Nast article. Hotels aren't just physically vulnerable: their wireless networks and point-of-sale systems have also experienced attacks.
In 2008, terrorists struck at two Mumbai hotels, killing about 200 guests and bystanders. The attackers simply walked into the hotels' lobbies and began lobbing grenades and firing automatic weapons. Even more disturbing was that the attackers had detailed knowledge of the hotels, and never allowed themselves to enter any areas where they could be cornered. This made them very difficult for Indian law enforcement to dispatch. While there isn't much you can do about a terrorist attack at your hotel, you can request a room away from the ground floors and the front of the hotel, where attacks are more likely to occur.
Many hotels use outdated credit card processing systems that store all of a customer's credit card information. When these antiquated systems are compromised, hackers have total access to all the information stored in them. One study, performed by a quality assessment firm called Trust Wave, discovered at least one million credit card accounts had been stored by major hotels in these types of attack-vulnerable systems. Hackers can also use malware, or malicious software, to glean credit card information during the processing phase. Customers using their credit cards anywhere in the hotel, not just to pay for rooms, are at risk.
You may have chosen your hotel because the rooms have Internet connections, but you should be aware that the data stored on your computer may be vulnerable to hacker invasion while you're connected. According to a Cornell study on hotel computer networks, some hotels are using older hub technology that is easily hacked, instead of safer routers or switches. Even hotels with encrypted wireless networks still showed some vulnerability, as the researchers were able to access information from private computers. This is especially concerning for the corporate traveler with sensitive company information on her laptop. If this is an issue for you, look to book hotel rooms with ultra secure virtual local area networks, also known as VLANs.