1 INTRODUCTION

2 THE MOBILE ADVERTISING NETWORK
2.1 The advertising ecosystem
2.2 User profiling
2.3 Targeted advertising
2.4 Ads selection algorithms
2.5 Ad billing

3 OPERATIONS OF ADVERTISING SYSTEM
3.1 Ad delivery process
3.2 Understanding ad network's operation
3.3 Ad traffic analysis
3.4 Characterisation of in-app advertisements

4 PRIVACY IN MOBILE ADVERTISING: CHALLENGES
4.1 Privacy attacks
4.2 Ad traffic analysis for evaluating privacy leakage
4.3 Inference of private information
4.4 User information extraction
4.5 Third-party privacy threats
4.6 Quantifying privacy algorithms

5 PRIVACY IN MOBILE ADS: SOLUTIONS
5.1 Private ad ecosystems
5.2 Data masking, anonymisation, obfuscation and randomisation
5.3 Differential privacy
5.4 Cryptographic mechanisms
5.5 Blockchain-based advertising systems
5.6 Comparison of various privacy protection mechanisms proposed in an ad system
5.7 The economic aspects of privacy

6 OPEN RESEARCH ISSUES
6.1 Diffusion of user tracking data
6.2 Complex operations of advertising system
6.3 Private user-driven mobile advertising systems
6.4 Private billing mechanism

7 CONCLUSION