Rowhammer is a hardware vulnerability in DRAM where repeated access to one memory row can corrupt data in adjacent rows. This can be exploited for unauthorized access, privilege escalation, or denial of service. While mitigations like ECC and Target Row Refresh (TRR) exist, their effectiveness against sophisticated attackers is questionable. Google has supported research and developed test platforms to analyze DDR5 memory and discover new attacks. Rowhammer exploits DRAM's need for periodic refresh cycles to maintain data, and aggressive access can cause bit flips. Attackers can leverage this by inducing bit flips and coercing the system to use those corrupted pages. Previous research has demonstrated Rowhammer attacks from software, making it a concern for multi-tenant environments like the cloud. Target Row Refresh (TRR) attempts to mitigate this by refreshing victim rows when adjacent aggressor rows are accessed frequently. However, attacks like TRRespass have shown TRR can be bypassed. Google collaborated on PRAC, a new mitigation that deterministically tracks memory row activations. Current DDR5 systems often rely on probabilistic measures like ECC and enhanced TRR, whose effectiveness against new attacks was unclear. Assessing Rowhammer requires understanding how mitigations work, how software accesses translate to low-level commands, and the role of host-side mitigations. Reverse-engineering proprietary DRAM mechanisms and analyzing DDR traffic necessitate specialized test platforms. Google partnered with Antmicro to create open-source FPGA-based Rowhammer test platforms for RDIMMs and SO-DIMMs. Using these platforms, researchers developed custom attack patterns that bypassed enhanced TRR on DDR5, leading to the first Rowhammer privilege escalation on a production desktop. Current mitigations are insufficient due to probabilistic countermeasures lacking sufficient entropy and ECC not being designed as a security measure. Memory encryption without integrity checks is also not a viable defense. Google continues to work on improving countermeasures and collaborates with partners to enhance analysis and testing, sharing findings with the broader ecosystem.