Attaining interoperability among these various protocols is always desirable so that applications of one network paradigm can avail the services offered by other networks. Therefore, by empowering sensor nodes with IP (Internet Protocol) features we get a unified and simple naming and addressing hierarchy and consequently we obtain a certain level of interoperability among different sensor network standards. With the help of IP in sensor networks, we can also utilize the tools already available for configuring, managing, commissioning or accounting of the IP networks. Since the underlying protocols are based upon IP, designer of new sensor applications can use existing standards to speed up the design and development process. The network of IP enabled USN devices is usually termed as IP-USN (IP-based Ubiquitous Sensor Networks).

One of the promising features of IP-USN is remote accessibility of sensor nodes. This enables remote monitoring and management of sensitive environments such as healthcare systems. Health care systems are connected to patients and monitor patient’s health, levels of medications and procedural outcomes. In such systems, it is not just sufficient to ensure confidentiality by encrypting the information sent out by the sensor nodes but it is also necessary to detect malicious or abnormal events in the system. Attacks and intrusions, for instance DoS (Denial of Service) or DDoS (Distributed DoS), against such systems may permit fatal damage to the health and safety of the patients. Such threats can be minimized by using firewalls and packet filtering.

However, mechanisms that attempt to detect intrusions when occurred are also inevitable so that the intruder cannot damage the system for a long duration. This problem of detection is not specific to IP-USN. A wide variety of literature is available on intrusion detection for both IP and sensor networks. However, IP-USN devices supports broader range of applications, for example, a few of the implementations of IP-USN now have the support of embedded web services [2]. Any possible security holes in the implementation of such applications can be eliminated by updating the firmware of the device or by using any signature based IDS which knows about the pattern of the request required to exploit the bug.

As updating firmware is not scalable, considering the large scale deployment of IP-USN, the later approach of signature-based IDS is an appealing solution.Moreover, other attacks Batimastat which exploit the weak hardware of the sensor networks are also possible in IP-USN. For example, IP layer usually works with available transport layer protocol. A few of the IP-USN implementations, such as Arch Rock [3], provide standard TCP and UDP protocols as transport layer for IP-USN; so that one can make connection easily to a sensor node to fetch the readings.