Tenable Holdings Inc

6. Acquisitions, Goodwill and Intangible Assets

In October 2023, we acquired Ermetic, an innovative cloud-native application protection platform company and a leading provider of cloud infrastructure entitlement management. The addition of Ermetic enhances our Tenable One

Exposure Management Platform and Tenable Cloud Security solution to deliver contextual risk visibility, prioritization and remediation across infrastructure and identities both on-premises and in the cloud. We acquired 100% of Ermetic's equity through a share purchase agreement for total consideration of $243.8 million, including $243.3 million in cash, net of $6.1 million cash acquired, and $0.5 million fair value of replacement equity.

In June 2022, we acquired Bit Discovery, a leader in external attack surface management (EASM). Adding Bit Discovery's EASM capabilities to our solutions provides customers with a comprehensive view of their attack surface and helps identify and eliminate areas of risk. We acquired 100% of Bit Discovery's equity for $43.8 million in cash, net of cash acquired of $2.0 million, through a share purchase agreement.

In February 2022, we acquired Cymptom, a platform that proactively measures, maps and prioritizes probable attack paths, and enables security teams to preemptively focus response ahead of and during breaches. Through a share purchase agreement, we acquired 100% of Cymptom's equity in exchange for cash consideration, net of cash acquired, for $23.0 million.

Purchase consideration, net of cash acquired, was allocated as follows:

We are still finalizing the allocation of the purchase price for Ermetic, which may change as additional information becomes available related to working capital and income taxes.

Acquired intangible assets and their estimated useful lives at the date of acquisition are as follows:

The results of operations of Ermetic, Bit Discovery and Cymptom are included in our consolidated statements of operations from the applicable acquisition dates and were not material. Pro forma results of operations are not presented as they are not material to the consolidated statements of operations.

We recognized acquisition-related expenses, primarily in general and administrative expense, of $9.5 million, $2.6 million and $6.9 million in 2023, 2022 and 2021, respectively.

Goodwill and Acquired Intangible Assets

The changes in the carrying amount of goodwill are as follows:

The excess purchase consideration over the fair value of acquired assets and liabilities is recorded as goodwill. The acquired goodwill reflects the synergies we expect from marketing and selling these new capabilities from Ermetic, Bit Discovery and Cymptom to our customers. The acquired goodwill is generally not tax deductible.

Acquired intangible assets subject to amortization are as follows:

Amortization of acquired intangible assets was $13.9 million, $11.4 million and $6.4 million in 2023, 2022 and 2021, respectively. At December 31, 2023, our acquired intangible assets are expected to be amortized over an estimated weighted average period of 6.2 years.

At December 31, 2023, estimated future amortization of intangible assets is as follows: