The rapid integration of Information and Communication Technologies (ICTs) and internet connectivity in academic environments has exposed institutional libraries to persistent cyber threats, ranging from unauthorized access to data breaches. This study investigated the security measures adopted to control cybercrime and the challenges mitigating their effectiveness in three tertiary institutions (Federal Polytechnic Damaturu, Federal College of Education (Technical), Potiskum and Federal University, Gashua) in Yobe State. The study adopted a qualitative research method and a multiple case study design, data was collected through semi-structured interviews with 6 participants that were purposively selected as a sample from twenty (20) Staff of elibrary/ICT staff and network administrators who frequently monitor clients who access online information from the three (3) tertiary Institutions with ICT/e-libraries and internet connectivity were considered as study participants. All the narratives from the 6 participants? were used for analysis. The data was analyzed using grounded theory Analysis. Findings revealed that while libraries employ fundamental security measures such as strong passwords, control software, and restricted network access keys, these protocols are currently ineffective against sophisticated cybercriminal tactics. Critical challenges mitigating the prevention cybercrime include lack of implemented cyber policies, inadequate technical expertise among staff, poor management attitudes, and insufficient funding for modern security infrastructure. The study concludes that the existing digital library environments are highly vulnerable to exploitation. It recommends the urgent development of a comprehensive cyber-security framework, the implementation of standardized cyber policies, and increased investment in specialized staff training and advanced security technologies, such as CCTV monitoring and system identification tracking, to ensure a secure and reliable digital research environment.