1. By Olga Gelbart rosa@seas.gwu.edu
Mobile Agents By
Olga Gelbart

2. What is an agent? A program (“software agent”), e.g.,
Personal assistant (mail filter, scheduling)
Information agent (tactical picture agent)
E-commerce agent (stock trader, bidder)
Recommendation agent (Firefly, Amazon.com)
A program that can
interact with users, applications, and agents
collaborate with the user
Software agents help with repetitive tasks

3. Is everything an “agent”?
Not all programs are agents
Agents are
customized
persistent
autonomous
adaptive

4. What is a mobile agent? Mobile agent: Agent that
Search
engine
Machine A
Machine B
Mobile agent: Agent that
migrates from machine to machine
in a heterogeneous network
at times of its own choosing

5. Definition
In a broad sense, an agent is any program that acts on behalf of a (human) user. A mobile agent then is a program which represents a user in a computer network, and is capable of migrating autonomously from node to node, to performs some computation on behalf of the user.

6. How it works?
Agent
Host A
Host B
Host C
Network

7. Mobile Agent Attributes
Code
State
Execution state
Object state
Name
Identifier
Authority
Agent system type
Location

8. Evolution of the “mobile agent” paradigm

9. Assumptions about computer systems violated by mobile agents
Whenever a program attempts some action, we can easily identify a person to whom that action can be attributed, and it is safe to assume that that person intends the action to be taken.
Only persons that are know to the system can execute programs on the system.
There is one security domain corresponding to each user; all actions within that domain can be treated the same way.
Single-user systems require no security.
Essentially all programs are obtained from easily identifiable and generally trusted sources
The users of a given piece of software are restrained by law and custom from various actions against the manufacturer’s interests

10. Assumptions violated by mobile agents (cont’d)
Significant security threats come from attackers running programs with the intent of accomplishing unauthorized results.
Programs cross administrative boundaries only rarely, and only when people intentionally transmit them.
A given instance of a program runs entirely on one machine; processes do not cross administrative boundaries at all.
A given program runs on only one particular operating system.
Computer security is provided by the operating system

11. Benefits of mobile agents
Bandwidth conservation
Reduction of latency
Reduction of completion time
Asynchronous (disconnected) communications
Load balancing
Dynamic deployment
Reduction of communication
Communication latency can be reduced since an agent can carry a sequence of service requests across the network, and there is no need to send these requests separately.
Moving the agent to the data source can reduce communication bandwidth. In this case, only the resulting data is transmitted to the client thus reducing the data before transmission.
Reduction of network connection time is also important. In the case of mobile code, a client needs to be connected only twice: while sending an agent and while receiving results back.
Asynchronous tasks
This goes in hand with reducing network connection time: after transferring a task to the network (via a mobile agent), a client can disconnect from the network and connect again only to receive results (which can be hours of days later). Clearly, this allows for execution on asynchronous tasks.
Dynamic Protocols and Intelligent Data
Some initial mutual protocol is required for the client and the server to start communication and for the server to receive a mobile agent. But after the initial communication is established a mobile agent can dynamically adapt to an appropriate protocol required for communication back to its home server. For example, an agent transmitting news updates can use a specialized multicast protocol for transmission to clients utilizing different communication protocol. An agent can dynamically adapt to this kind of situation.
Software Deployment
Mobile agents can be used for automation of software installations and upgrades.
Temporary Applications
Java applets can serve as examples of temporary applications: small applications, which do not require installation, can be temporarily downloaded and discarded when their task is finished. Route planners for travelers are examples of such applications.
Distributed Heterogeneous Computing
Mobile agents can provide a communications infrastructure for tasks in a distributed environment. For example, agents can collect data on one node and transfer is to another (an agent collects raw data from a system and submits it to a graph plotter server – can be faster than transmitting a whole image).
Scalable applications
As an example, we can look at a searching program. In a typical client-server situation, retrieved documents (from various data sources) are transferred to the client and sorted or filtered there. The client as part of the network creates a bottleneck. Mobile agents can perform content-based filtering on the spot and also get rid duplicate or redundant documents before transferring results back to the client.

12. Reason 1: Bandwidth conservation
Text documents,
numerical data, etc.
Dataset
Client/Proxy
Server
Dataset
Client/Proxy
Server

13. Reason 2: Reduce latency
Sumatra chat server
(a “reflector”)
1. Observe high average latency to clients
2. Move to better location

14. Reason 3: Reduce Completion Time
Efficiency
1. Send code with unique query
Low bandwidth channel
Mobile users
3. Return requested data
2. Perform multi-step
queries on large, remote,
heterogeneous databases

15. Reason 4: X X X X Disconnected communication and operation Before
After

16. Reason 5: Load balancing
Jobs/Load
Jobs/Load migrate in a heterogeneous network of machines

17. Reason 6: Dynamic Deployment
Unique needs:
maps,
weather,
tactical updates....
Command post
Tactical updates
Map, terrain databases
Weather

18. Threats posed by mobile agents
Destruction of
data, hardware, current environment
Denial of service
block execution
take up memory
prevention of access to resources/network
Breach of privacy / theft of resources
obtain/transmit privileged information
use of covert channels
Harassment
Display of annoying/offensive information
screen flicker
Repudiation
ability to deny an event / action ever happened
Destruction of:
files on the internal / external data storage. These files can be an kind ranging from configuration (operating system specific) to data files. This can be either deletion of corruption.
Hardware : hardware-intensive executions which eventually may destroy it
destruction of current execution environment: processes, stack, etc
Denial of service:
block execution of other processes
take up all memory by replication
prevention of access to data resources internally or from the network (a host is a server on some kind of a network)
Breach of privacy & theft of resources:
Malicious mobile agents can obtain privilege levels higher than required for an agent execution and gain unauthorized access to private information stored in internal data storage or external data storage (which could be a disk array or a database server). This private information (such as medical data or financial records) can then be take by the agent when it leaves and transmitted.
Secret recording from a computer microphone and the following transmission of information to an unauthorized cite.
Us of covert channels to transfer information to an unauthorized cite.
Harassment:
Display of annoying or offensive materials onto computer screen, periodic screen flicker are more damaging to the human user than to the computer itself, but should still be considered, since this is a threat to human working conditions. It’s dangerous especially if the screen flicker is introduced at a frequency known to cause seizures in sensitive people.
Repudiation:
ability to deny an event ever happened and get away with it. This is more of an “after effect”, but is still important. If an unwanted event happens, there should be some way to prove that it was caused by a malicious mobile agent.

19. Protection methods against malicious mobile agents
Authenticating credentials
certificates and digital signatures
Access Control and Authorization
Reference monitor
security domains
policies
Software-based Fault Isolation
Java’s “sandbox”
Monitoring
auditing of agent’s activities
setting limits
Proxy-based approach to host protection
Code Verification - proof-carrying code

20. Threats to mobile agents
Denial of service
Unauthorized use or access of code/data
Unauthorized modification or corruption code/data
Unauthorized access, modification, corruption, or repeat of agent external communication

21. Possible attacks on mobile agents
Denial of service
Impersonation
Host
Agent
Replay
Eavesdropping
Communication
Code & data
Tamper attack

22. Protection of mobile agents
Encryption
code
payload
Code obfuscation
Time-limited black-box security

23. Application: Technical reports
GUI on
home machine
Machine n
Machine 1
...
1. Send agent
2. Send child agents / collect partial results
3. Return merged and filtered results
Dynamically selected
proxy site

24. Application: Military
Wired network
Wireless
Network
Technical
specs
Troop
positions
Orders and
memos

25. Application: e-commerce
Arbiter
VendorA
VendorB
Bank
Agent
Agent
Yellow pages

26. Mobile agent systems

27. More examples and “bots”
Tryllian mobile agent system
Bots
mysimon.com
amazon.com - customer preferences

28. Current trends lead to mobile agents
Increased need
for personalization
Server-side
Information
overload
“Customization”
Mobile code
to server
or proxy
Too many unique,
dispersed clients to handle
Diversified
population
Proxy-based
Multiple
sites to visit
Mobile
Agents
Bandwidth
gap
Avoid large
transfers
Mobile code
to client
Avoid
“star”
itinerary
Mobile users
and devices
Disconnected
Operation
High
latency

29. Migrating to migrating code
Applets
Proxies that
accept
servlets
Services that
Proxies
provided
by existing
ISP’s
Mobile
Agents
Intranet
Internet

30. Conclusion: Cons Security is too big a concern
Overhead for moving code is too high
Not backward compatible with Fortran, C ….
Networks will be so fast, performance not an issue

31. Conclusion: Pros
A unifying framework for making many applications more efficient
Treats data and code symmetrically
Multiple-language support possible
Supports disconnected networks in a way that other technologies cannot
Cleaner programming model

32. For more information... Mysimon.com
D’Agents:
Tryllian:
Aglets: